I keep running into this problem

[DogterB]

Problem: brown/rusty spots on leaves, between veins. Seems to be upper fan leaves, but spots show up wherever. I seem to run into this shortly after flowering commences, but this run I have one showing some just before flower. Not all plants are affected, but a couple are.

Medium/grow method: DIY octopot wannabe type setup. Amended soil, only add in teas or top dress.

Feed: and supplements used: Here's my soil mix
1/3 coco coir
1/3 potting soil
1/3 composted cow manure

Amendments:
60% earthworm castings
20% boxed amendments: 1/2 and 1/2 of Dr. Earth's Homegrown & Flower Girl
10% lime
10% epsom salt

Mixed and let cook for several weeks, first time trying this mix.

water source: tap water that has been allowed to sit open 24+ hours. SIP setup, between 6 plants they pull in about 3 gallons per day

Strain/age:
6 total strains but the ones showing signs are: ogreberry (20twentymendocino), afghan skunk (Linda seeds), and purple kong (rocbudinc)

light used: One side of the 4x4 tent has an HLG 350R and the other side has 2x HLG QB96s each ran on a HLG-185

Climate: climate maintained at 86F and 70% rh at this time

Additional info: I have run into this problem several times and don't know what's going on. Hoping for some advice and what I should do with the mix to prevent this in the future. Any advice is appreciated

 

[MIAutomatic]

You have so many custom variables it’s hard to make a reliable diagnosis, but there is some type of lockout or deficiency. It could be a P deficiency or a calmag issue, or a number of other things. PH of water and runoff and PH/EC of runoff will be useful diagnostic data points.

These are some other things going on in your tent that are not the main problem, but I am sure are not helping the situation. Your humidity and temps are just a little high high 70s - low 80s and 55-60% humidity would be better and remove one source of potential stress. Your fan placement is also not ideal and could be causing some wind stress to the plants, and also additional terpene loss once heavy flowering kicks in. It’s generally not a good idea to point fans directly at the canopy, but to keep air moving right above and below the canopy. The leaves should move with a light breeze, but not have fans pointed right at the leaves or flowers, at least not at the distance you have them placed.

This may not be the advice you were looking for, but hopefully some of it is helpful.

Good luck!

 

[DogterB]

You have so many custom variables it’s hard to make a reliable diagnosis, but there is some type of lockout or deficiency. It could be a P deficiency or a calmag issue, or a number of other things. PH of water and runoff and PH/EC of runoff will be useful diagnostic data points.

These are some other things going on in your tent that are not the main problem, but I am sure are not helping the situation. Your humidity and temps are just a little high high 70s - low 80s and 55-60% humidity would be better and remove one source of potential stress. Your fan placement is also not ideal and could be causing some wind stress to the plants, and also additional terpene loss once heavy flowering kicks in. It’s generally not a good idea to point fans directly at the canopy, but to keep air moving right above and below the canopy. The leaves should move with a light breeze, but not have fans pointed right at the leaves or flowers, at least not at the distance you have them placed.

This may not be the advice you were looking for, but hopefully some of it is helpful.

Good luck!

Appreciate the input! Yeah, lots of variables at play here. I don't pH my water as I've been told with living soil pH'ing is not necessary. This is a SIP, so there is no runoff to test. I love this setup but it does make it hard to do any testing.

As for temp, this run I've been trying to maintain 86F because I saw a few papers saying that 86 is the optimal temp for cannabis growth. I've been keeping the temp there and altering the rh based on a VPD chart for each growth stage. Previously I have kept it lower than that, more in the mid 70's. Whether this is correct or not, I have no clue.

Yeah the two fans are not ideal, I agree. There is definitely some signs of wind stress on some of the leaves right up next to the hanging one. Should I lower the hanging fan to be blowing below the canopy or try and raise it up above if I can? There was an attempt the keep the lower parts cleared for airflow but with my schedule they got out of hand pretty quickly. The hanging one is an oscillating fan and the motion causes it to swing back and forth on the rope and it covers the tent. The smaller one in front is pointed to the shorter ones to keep some air flow because they are really thick. The plants on the left side of the tent all blew up on me and it's getting really crowded in there.

Again, thanks for the feedback! I think before next run I'm going to cut back to 4 5-gallon pots instead of 6 3-gallons, and put up a net and try to scrog it all. I'm just trying to get it all figured out still, but aren't we all. I've had this exact leaf discoloration when using other store bought soils too, always at right about the same time.

 

[MIAutomatic]

Appreciate the input! Yeah, lots of variables at play here. I don't pH my water as I've been told with living soil pH'ing is not necessary. This is a SIP, so there is no runoff to test. I love this setup but it does make it hard to do any testing.

As for temp, this run I've been trying to maintain 86F because I saw a few papers saying that 86 is the optimal temp for cannabis growth. I've been keeping the temp there and altering the rh based on a VPD chart for each growth stage. Previously I have kept it lower than that, more in the mid 70's. Whether this is correct or not, I have no clue.

Yeah the two fans are not ideal, I agree. There is definitely some signs of wind stress on some of the leaves right up next to the hanging one. Should I lower the hanging fan to be blowing below the canopy or try and raise it up above if I can? There was an attempt the keep the lower parts cleared for airflow but with my schedule they got out of hand pretty quickly. The hanging one is an oscillating fan and the motion causes it to swing back and forth on the rope and it covers the tent. The smaller one in front is pointed to the shorter ones to keep some air flow because they are really thick. The plants on the left side of the tent all blew up on me and it's getting really crowded in there.

Again, thanks for the feedback! I think before next run I'm going to cut back to 4 5-gallon pots instead of 6 3-gallons, and put up a net and try to scrog it all. I'm just trying to get it all figured out still, but aren't we all. I've had this exact leaf discoloration when using other store bought soils too, always at right about the same time.

I think that sounds like a good plan for the fans, and also a good idea to cut back in the number of plants in the tent. Having a bit more space for the stretch their legs will help with airflow and humidity. As far as VDP goes I am not gonna go look at a chart, but 70% rh is probably about right for 86 degrees, but 70% humidity with flowering plants in a tent seems risky to me. Airflow can counteract temperature and humidity to a point, but those levels seem a little high for my comfort. I live in Michigan where I am always battling large humidity swings all through spring and summer, so I always keep things on the lower side just to be safe.

 

[DogterB]

I think that sounds like a good plan for the fans, and also a good idea to cut back in the number of plants in the tent. Having a bit more space for the stretch their legs will help with airflow and humidity. As far as VDP goes I am not gonna go look at a chart, but 70% rh is probably about right for 86 degrees, but 70% humidity with flowering plants in a tent seems risky to me. Airflow can counteract temperature and humidity to a point, but those levels seem a little high for my comfort. I live in Michigan where I am always battling large humidity swings all through spring and summer, so I always keep things on the lower side just to be safe.

After checking my chart, you’re right, I need to drop the rh a bit with where they are at. I’ll have to adjust my inkbirds a little tonight after I get out of school. Damn education is taking up all my time lol

 

[automan2]

I'd first look at your medium mix. Coco and soil don't usually perform best at the same Ph value.

 

[Bill.de.Cat]

What is the source of your tap water? City or well...some cities use chloride or chloramide or something like chlorine but it doesn't evaporate out and could cause issue even sitting out for 24 hrs. Well water can cause problems due to minerals as well....one reason you see us using RO or distilled water, we know what's not in it.

 

[DogterB]

What is the source of your tap water? City or we'll...some cities use chloride or chloramide or something like chlorine but it doesn't evaporate out and could cause issue even sitting out for 24 hrs. Well water can cause problems due to minerals as well....one reason you see us using RO or distilled water, we know what's not in it.

Water is city water. I used to use RO water back when I first started, but keeping that much water on hand was difficult. We have a Berkey filter for our drinking water, think I should switch to that? It'll be hard to get enough water through the filter every day...

 

[Bill.de.Cat]

Any idea what they use for sterilization and did you have this same problem using RO?

 

[DogterB]

Any idea what they use for sterilization and did you have this same problem using RO?

No clue about sterilization, though recently they have been getting hell about forever chemicals. Yeah, had issues when using RO, but I was also using FFOF for soil