Indoor Purple punch auto getting sickly

[Boradan]

Purple Punch auto from Seedstockers.
7 weeks old and just starting into flower.
Canna Coco coir and perlite 60/40 mix
12 Litre Airpots
Full Canna nutrients range.
pH 5.8 to 6.0
EC 1.2 (only the nutrient EC, base water EC of 0.4 not included).
22c to 25c temperature.
RH 50%
18/6 lights using a Mars Hydro FC-E4800 at 75% and 16"

Some leaves starting to yellow (veins still green)
Mostly older leaves affected.
I increased the nutrients slightly thinking it was nitrogen Def initially, but that seems to have led to a few tips curling down, so I dropped the EC back again.
Possibly magnesium deficiency and I have some Epsom salts on hand incase that is the case.
The pictures are under 2 different lighting - just the camera flash, and then under the Mars Hydro.

 

[Bob's Auto's]

I think you are right with the Magnesium def. Been looking at those pictures for a while now and I'm 90% sure it's Mg that's being locked out, but...I don't think you don't have enough Mg in your medium, rather the other way around. The fact that the leaves don't show rusty spots on them makes me lean that way.
What I would do is...Drop the EC of your nutrient solution to 800. Why...Looking at those dark leaves they're getting to much of a good thing. This can lock out some nutrients and look like a def.

Next thing to know (and you already provided plenty of info). Do you feed with 20% run-off? Coco likes to be treated like hydro and needs to be kept constantly wet, but to prevent salt build-up you must water them with nutrients until you recuperate 20% through the bottom. A waste I know, but that's why I switched over to BioTabs. A real stoner way of growing...I must admit

 

[Boradan]

Ta for the input.
I am feeding to waste, around 15 to 20 percent runoff.
I actually just prepared a lower dose solution as a precaution.
Also dechlorinating additional water to flush with first.

 

[Bob's Auto's]

Ta for the input.
I am feeding to waste, around 15 to 20 percent runoff.
I actually just prepared a lower dose solution as a precaution.
Also dechlorinating additional water to flush with first.

Let us know how it turns out brother

 

[MIAutomatic]

I would back off on that nutrient concentration. Your total EC of 1.6 is pretty high IMO. I also use full canna line in coco and 1.65 total EC is where I max out most grows with healthy plants in peak flowering. Much higher than that and I start to see build up in my runoff even with 20% fertigation.

With your base water at 0.4 EC plus the calmag from A&B the amount of calcium or magnesium shouldn’t be an issue, but you are probably getting lockout from a buildup of macro nutrients. 0.4 EC is what I use for my base water and as long as the nutrients are balanced I never have calmag issues.

First check your runoff EC and if it is high I would reduce your overall feeding solution to 1.2-1.3 EC and see if that helps to bring things back around.

good luck!

 

[Boradan]

I would back off on that nutrient concentration. Your total EC of 1.6 is pretty high IMO. I also use full canna line in coco and 1.65 total EC is where I max out most grows with healthy plants in peak flowering. Much higher than that and I start to see build up in my runoff even with 20% fertigation.

With your base water at 0.4 EC plus the calmag from A&B the amount of calcium or magnesium shouldn’t be an issue, but you are probably getting lockout from a buildup of macro nutrients. 0.4 EC is what I use for my base water and as long as the nutrients are balanced I never have calmag issues.

First check your runoff EC and if it is high I would reduce your overall feeding solution to 1.2-1.3 EC and see if that helps to bring things back around.

good luck!

Cheers bud

I dropped the ec and gave some foliar of Epsom salts (as well as a touch in the water) and all is hunky dory now.