Calcium deficiency?

Hey yall i could use some help, this is only affecting 2 out of 7 plants, the others are looking mint. I'm noticing rusty spots on the edges and in between leaf veins on the upper canopy(lower leaves are mostly unaffected) of these two plants.

I'm in a peat based soilless mix. Been feeding 2 ml calmag and around 4-5 grams mega crop the past couple weeks. Tap water is at 100 ppm and the pH naturally goes down to around 6 when I add nutes. They are at almost 4 weeks now.
This looks like a very specific problem to me, not a combination of things (could be wrong). I was thinking nute burn but I thought the tips should be more burned up before it spreads to the edges? Any help is appreciated thanks!

I would say Yes that COULD be the start of Cal issue. CalMag should be bumped up. I use peat as well but I use peat with perlite in 50/50 ratio. The peat itself is very acidic and will drop your root zone PH by a whole point in some cases. Do us a favor and give us a runoff test and give us the PH and PPM going In and well as coming out. For example for my peat/perlite mix I have to PH my feed at 6.9 and it comes out at 6.0!

Word I'll do a soil slurry test when my dehumidifier fills up with water. My mix is about the same as yours 50/50 peat perlite. I'm thinking since they've been in these small 3 gals their whole lives the lime is starting to run out dropping the pH. If I can't think of anything else I might just topdress with some oyster shell flour and call it a day lol

word. If that's the worst that it gets then you are going to be good to go anyway. Nothing there looks too bad. I've had the same spotting with PH issues in Peat when I don't get my rootzone ph right. I prefer Peat over COCO actually but yeah the acidity has to be accounted for. Personally I will add my Bloom, my Mag supplement, then a pinch of baking soda and then my pH UP until I am at 6.9 or 7. My runoff is always 5.9 or 6 with this setup and my plants love it. Check out my journal with peat over at https://www.rollitup.org/t/tga-testers-tasmanian-skunk-and-cherry-cordial-og-picture-heavy.959757/

So after a soil slurry test the pH seems pretty normal, between 6 and 6.2. I think I'll just bump up the cal mag to 5 ml per gallon. They otherwise seem pretty happy with the level of nutes I'm giving them. And they're bubba kush crosses which can be kinda finicky, my other plants look absolutely fine.

Holy shit I'm retarded. I added another quantum board about 5 days ago to increase wattage. Plants started showing symptoms about 2-3 days after that. Qbs and cobs are known to make plants uptake more calcium. Its definitely a calcium deficiency from increasing the wattage. Glad I got that shit figured out.

dubekoms said:

Holy shit I'm retarded. I added another quantum board about 5 days ago to increase wattage. Plants started showing symptoms about 2-3 days after that. Qbs and cobs are known to make plants uptake more calcium. Its definitely a calcium deficiency from increasing the wattage. Glad I got that shit figured out.

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I've found the need to add Ca/Mg to almost any nute under my cob led's. Never really needed to with my HPS/MH though.

HydroRed said:

I've found the need to add Ca/Mg to almost any nute under my cob led's. Never really needed to with my HPS/MH though.

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Yup I remembered we talked about this a few days ago which led me to my "eureka" moment. How much calmag are you running? The affected plants needed watering last night anyways so I bumped it up from 2ml to 5ml per gallon. They don't seem to be getting worse today but its a little to early to really know.

dubekoms said:

Yup I remembered we talked about this a few days ago which led me to my "eureka" moment. How much calmag are you running? The affected plants needed watering last night anyways so I bumped it up from 2ml to 5ml per gallon. They don't seem to be getting worse today but its a little to early to really know.

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I've never needed more than 2 ml or so per gal with any nutrient so far but Im only under a soft 400W at one time with my led's so its never been anything "aggressive" when the onset of deficiency begins. Recovery has always been far quicker than the onset im my experience too.

I'm not sure... But could it be a phosphorus def?? Purple stems and brown spots...
Though I get similar brown spots from ph issues.. Looking good either way. Good luck