what's causing this?

I'm really lost here! I have been growing this way for years now, this started to appear on leaves about a 3-4 weeks into flowering, started like rusty to white spots, and then progressed. There are no pests and PH is always within range. I changed the res only 2 days ago, i really was optimistic that this will be solved, but I opened up today to see that things are still going downhill.

I looked and searched for answers, everywhere i look, it definitely resembles Calcium deficiency, only thing is, i have plenty of Ca in my fresh res, and I lowered the K levels a bit to prevent any Ca lockout.

I am really clueless here. I am looking for the reason that is locking the Ca out, other that K overdose? I added H2O2 to remove any scale buildup on my rocks but i went low with the dosage. I am running out of options, I almost tried everything, I have a calcium foilar spray but I don't like to spray anything in flowering especially with the leaves going unhealthy, but I might just do that. I also am considering adding more h2o2, maybe I need to clear up more scale from the root surface or something?

I need advanced knowledge, this is definitely nothing straight forward, as I have an entire greenhouse of veggies that are growing amazingly well with the same ferts. my calcium source is calcium nitrate, it is highly soluble, bu I read somewhere that scale buildup from non-soluble calcium that is present in source water, can make sort of a filter that locks Ca out. Could this be the issue?

Come on MP experts, I need you to scratch your heads with me PLEASE! thanks all.

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Total shot in the dark. Have you checked this against either another PH meter, or PH drops? Not sure if your meters is acting odd.

Is this the first time with this strain? It looks like early onset necrosis.

Still better looking than what I had going on a couple months ago (I hate soil lol!)

Good luck, and hopefully an expert comes in here! :aok:

DGF i use reliable ph drops and yes i tried a fresh bottle, i opened it up just to see if the older one is reading bad, and it's not. also i tried to lower and raise the ph, i have been trying to solve this for some time. it is not the first time with this strain. Today I added a good dose of H2O2, hoping that it helps. What do you think about foilar calcium feeding? i'm thinking maybe i should do that, but i really don't like to spray my buds with anything even if not toxic, i don't want to be smoking residues of anything. what do you think?

I wouldn't spray my buds at all (sure during veg and up to 2 weeks into flower, but not beyond that), so I'm of no use there. It really seems like you have things sorted out but it's crazy seeing the issue, especially since you've already dosed with Cal-Mag. Are you seeing new leaves getting worse each day? I'm sure you're not looking at the same bad leaves thinking "oh darn, they aren't looking any better"... I believe you're more of an advanced grower than that hahahah! I hate to even ask, but I'm just "going down the list" in my head, you know? Trying to help as best as my noobness allows.

I would wait 24-36 hours after your H202 dose before trying anything else. Remember, as you know, don't try too many things at once. So, I know you know that we'll go past that.. I wouldn't foliar spray. At this point, I would do your best to help them finish as strong as they can. You've seen my crap looking stuff in soil over the last few months, and there was nothing I could do. In the end, I think it was temps locking out various elements. )Soil is sooooo fickle, grrr!!) Either way, I would just finish strong the way you are... and not foliar. I think the H202 should help. What's your PH sitting at and what does "the swing" look like over 48-72 hours? What are your PPM's? (sorry if you've said this recently.. reanswer if so lol). Also, have you tried running water only in the res for 24 hours or so? A "mid-run" flush is quite a good thing, if you're DWC. I think you're DWC right? I can't remember... stupid memory! :rofl:

what else are you feeding the plants?

DGF you thinking out loud with me always helps, but yeah, i went down that list already, and i must be missing something. i didn't do a mid run flush, i am in flood and drain, i never liked to flush with only water. my ph drifted from 5.5 to 6 overnight, and ppm dropped from 1050 to nine hundred something i figured theyre feeding but not looking good, i topped and didnt check since, but they should be anywhere in the 1100-1200 and added ph down but also didn't check yet. i will check in a bit when the lights turn ON... thanks for thinking with me, this problem is starting to give me a headache, it's frustrating, like every day, i figure that i found out the cause, i adjust, and wait, then see it going backward, again and again, lol i'm out of bullets here haha
Grower13 glad to see you here buddy i feed with the following: Calcium nitrate, potassium nitrate, mono-potassium phosphate, magnesium sulfate amd trace element mix. I also use potassium sulfate, but chose not to in this res because i was trying to cut back on potassium use to prevent Ca lockout, as that was one possible reason.

You know what?, I am optimistic again, i am 99% sure that it is Ca and i closed in on its cause, that H2O2 should help, I really hope so, it should descale all the useless stuff from my roots, and let the Ca in. i really think and hope that i found it. Ca can get locked out from high K, PH off, OR too much scale on the roots. I do flood and drain and the roots are in air so maybe the evaporation is causing scale buildup... shall we, do our routine cannabis church prayers? :48:

I agree, H202 should help this situation.

By the looks of it, not only are they feeding, but they are screaming for more food! 5.5 - 6.0 over night? And with PPM's dropping? Seems they are eating like CRAZY. Up the dose IMO to around 1300. You're using HPS yes? 1300 - 1400 SHOULD be safe, strain depending.

How much have you run this cut did you say? (I suck at memory and re-reading)

as far as your into flowering stage the only way to tell if the nutrient lockout/deficiency as been corrected is by bud growth and current nutrient use......... I think a build up of salts or some conflicting nutrient amounts or types cuased your issue.......... but it looks like you had more than just one thing locked out.......... based on the leaf pics it was multiple lockouts.imho

Hate this is happening Zem, you all have covered anything I could have thought of, so I'm here just to see what the outcome is, green mojo Zem.

I checked on them, I am unsure yet, but i think that they might be bouncing back as i noticed that the whole canopy is somewhat better.
DGF I think that I will go ahead and further raise the ppm tomorrow. theyre growing under 2x400w hps, i did this strain many times before.
Grower13 I think that the Ca lockout could cause other elements to be useless for the plant, but i saw the Ca deficiency symptoms very prevalent

can we get a pic of the entire canopy?...room...I see a few things myself..but have to ask...whats the "Entire" picture look like..I am sorry..I wont shoot in the dark as I know would send ya wrong..I wish ya the best

yep yep... now i'm sure that they're better. the h2o2 seems to have heled

That's good news

Thanks Duck I just made an update with pics in the journal http://www.marijuanapassion.com/forum/showthread.php?t=70982&page=4

Nice, great to hear! :aok: