Dark spots and light leaves

[Haunts]

Problem: Leaves are getting dark spots, yellowing and going crispy.
-Medium/grow method: Plagron Light soil
-Feed and supplements used: I've been following tangs easy grow schedule and never any problems with it before https://www.autoflower.org/threads/tangs-easy-auto-feeding-schedule.47290/
-Strain and age Sweet seeds cream caramel at days 50
-Climate: 24/7 light schedule, temps 25C, RH 40%
- Light used: 150w hps it's about 5 inch from the top of canopy
-Additional info: The problem started about 10 days ago and i've tried giving them a couple doses of cal/mag. Should I perhaps try flushing?

 

[Waira]

:smoking: Haunts buddy, apologies for this one slipping by! ... if this happens, holler sooner, even hit RP's,....

...Hmmm, I'd say a couple things going down here,... The yellowing on the upper leaves, with the strong "zebra" effect is looking like Zn defc. to me (Fe defc. often co-happens)... overall yellowing could be a combo of P defc., which the course spotting is from (though sometimes Ca can mimic this as well), and maybe some heat/light intensity stress (curled margins, up-pointy "teeth", even on greener leaves),... 5" is way too close for even a 150w HPS,... So question is why, with the defc.'s,... do you monitor in-pot pH? AN and other self- buffering nutes will handle pH in solution only, they do not have the chops to deal with all the other influencing factors that affect pH in pot, so complacency about this using AN or whatever often can bite one in the rear! And you know, pH is everything for nutrient absoption! For ZN, it's high pH that locks it out, and I'm betting if anything the soil is low in pH, so likely it's a simple lack-of defc.; fix this with a dedicated micronutrient supplement, like Earth Juice Microblast; the Ca-Mg you put in will take a few days to get busy (if this is, in part, Ca defc.), and if you have a PK booster, try adding that in now to up the P,... I really need an in-pot pH to be sure, but I'm betting you don't have a good pH soil probe (Accurate 8 makes a good one), so it might default to the lousy run-off method... we have an improved method here as a sticky article in the Infirmary, above this section,.. check it out! I don't recommend flushing unless we have some sort of clue about the pH in there,...

 

[Haunts]

Thanks Waira for looking at this. I do have an accurate 8 probe but ive never actually used it because its a beast compared to my 4L pots. Will it do damage to the roots? I need a little guidnce as well. Do i just push it all the way down into the bottom of the pot? Should i do it after ive watered them or before? And do i push the button thats on the probe for the reading or is that to take the moisture reading?

 

[Waira]

- excellent! did you read the instruction on the packaging? Don't sweat a little root damage, it's hardly enough to bother them, nothing compared to the defc.'s,...
> always buff the probe tip clean with that pad before use, and wipe it down with a paper towel... never immerse in liquids, BTW!
> best results come from well moistened soil/medium, not soaked, and definitely not dry-ish... this makes for less accurate readings,... don't use it right after feeding either, you just added a pH altering solution to the soil, so this will skew the results temporarily,...
> I shoot for at least half way down, a couple inches or so from pot edge, no where near the main tap root close to the plant, pushing with a gentle back and forth twisting.. you'll see the dial go nuts while doing this, ignore it... let it sit for 2-3 min. to stabilize, then read...
> remove and clean with a damp paper towel or something, then store wrapped up and protected from damage,...
... let me know your reading!

 

[Haunts]

Thanks for the guide mate, I gave them a feed yesterday and have just taken a reading and its showing 6.9.

 

[Waira]

not so bad Haunts! What's your water source? To get the pH down, gently, start adjusting your feeds and water to low 6's pH,... if you're using tap water that has significant hardness (ppm's), you can either switch to a lower ppm source, like the self fill units at grocery stores, etc., or RO/DI and blend it,... even using citric acid (canning section should have pure stuff) will bring the pH down; from my experience it takes only tiny amounts with 170+ ppm tap water, like 1/4tsp/gal! ...alas, if you weren't in bloom, this fix on the defc.'s could be much easier with foliar, and using Optic Foliar's Transport as a carrier for the Ca-Mg and micro's,... Has the progression slowed at least? The more hammered leaves may tank out anyway, no stopping that especially at this stage,...

 

[Haunts]

I'm using tap water so i'll pick up some citric acid to try and bring the ph down. I was always under the impression that you didnt have to mess with ph in soil grows i'm guessing thats not the case? If i'm checking the ph before feeding the plant do i still need to check the soil ph as well and what is the ideal ph 6 - 6.5?

 

[pop22]

I recently read that this type of yellowing and striping is cause by PH being too high and causing various deficiencies

 

[pop22]

Thats a common misconception caused by not knowing you water's content and ph. My tap water is so bad it KILLS my plants! I have to use RO water. In soil if your water ph is 6.5 - 7.0 and the ppm is 100 - 150 your probably good. Tap water ph changes often though, check tour water regularly and you'll rarely have to ph your soil.

I'm using tap water so i'll pick up some citric acid to try and bring the ph down. I was always under the impression that you didnt have to mess with ph in soil grows i'm guessing thats not the case? If i'm checking the ph before feeding the plant do i still need to check the soil ph as well and what is the ideal ph 6 - 6.5?

 

[Waira]

...yup, in soil, pH monitoring is critical, always! Only if you were using a quality true living organics (TLO) soil would pH not be as big of a concern,... but reg. soil grows, always test, and best way to keep it stable is to adjust both water and feeds accordingly,... test the soil, then if it's off, like yours --a bit too alkaline-- you can adjust the water and feeds down in pH some to help correct it and keep nutes fully available,... in your case fortunately the nute soln. will be acidic by nature,... question is, what's you tap water like for ppm's and pH? See, like pop22 mentioned, if it's very hard and full of minerals (CaCO3 mainly) it'll be a bitch to control pH with, plus cumulative mineral inputs will fuck with other nute's uptake down the road,... it's the carbonate anion that's involved with pH buffering in water, so the harder it is, the more carbonate will be acting on the pH and can cause it to rise out of optimal range, and resist correction! get us that water info mate,...