Having trouble narrowing down a cause

So I have 5 ak xtrm plants that are 37 days in veg from seed the oldest set of fan leaves yellowed up at like maybe week 3 and dropped figured out it was a magnesium deficiency so switched to RO water and started adding cal mag @ 2ml per lt every watering and feeding. Everything returned to normal and I was watching my fan leabes Slowly start to untwist. Now this morning I wake up and see my oldest set of fan leabes yellowing from the tip in they look like a light green faded color. Almost like an N deficiency. But I actually dropped my nutes from 1ml per lt (an sensi grow a and b) to .75 ml per lt last week bc the tops were clawing a tiny tiny bit so I thought there was to much. Ppm w cal mag is at 450 the plants are about 15" tall in 7 gal pots after being topped once 3 weeks ago. Ph is at 6.5 ish roots organic soil 707 and 400 watt hps is 18 inches from canopy but not air cooled (4 total in room) temps have been swinging a bit lately bc my heat broke on Friday and I had to get space heaters and it's been extremely warm here last couple days and now back to 30 degrees outside well warm for New England (45-50 degrees hAha) and rh is always low around 30 in room all the time unfortunately

I should mention only 2 plants are doing it and they are either in al promix ultimate or half roots half promix (bc I ran out during transplant and they discontinued the promix at the hydro store

MattMA said:

View attachment 3371081 View attachment 3371082 View attachment 3371084 I should mention only 2 plants are doing it and they are either in al promix ultimate or half roots half promix (bc I ran out during transplant and they discontinued the promix at the hydro store

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Seems nute burn to me if u said u added cal mag before and or Heat problem but umm yea. So far is all i can chim in give us an update couple more days pls,


-Jugz

I don't think it's nute burn bc the yellowing seems to spread from the tip up the leaf it's a light green color now but seems like it will fade to yellow

MattMA said:

I don't think it's nute burn bc the yellowing seems to spread from the tip up the leaf it's a light green color now but seems like it will fade to yellow

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Maybe im wrong, but I believe lower branches are the weakest and cant handle the same as the bigger more strong looking branches, nute burn looks like that, again keep an eye on it. U doing fine in the steps u took before.

Right on thanks I'll def keep looking for any signs of spreading or brown spots or anything

roots burned every plant i ever put in it.... went back to my happy frog for dirt

MAybe they are getting burnt it's crazy bc I'm using less then 1/4 strength nutes and the pots that have only roots 707 in them aren't showing the signs it's the one that is all promix ultimate organic and one w a mix of that and the 707

I just looked at them again tonight when the lights turned on after I got home from work... Way more yellow.... I bet they will be completely yellow in 2 days or so and they feel all dry and rough ... Almost like they will crumble if I rub them together ..... I'm gonna lollipop the plants on Sunday anyway but I don't want this getting any higher up the plant

MattMA said:

I just looked at them again tonight when the lights turned on after I got home from work... Way more yellow....

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Need to see photos showing the entire plant. If these are just lower leaves, they tend to die off anyway.

All I see is mg def. If you interpreted nute burn and reduced nutes you could now be seeing general deficiency.

What is the ph and ppm of your runoff? Do you get runoff when you feed? How much? Could be salt buildup. But, your plants should improve feeding 1/4 strength.

Without seeing more of the plant, I think you should feed full strength with 25-50% runoff. A mini flush while feeding. A lot of runoff is always a good thing to do. I'm just not sure whether full strength nutes are a good idea without seeing the entire plant (and knowing runoff ppm and ph).

Ya I was just looking at them and athought I am supplementing cal mag w my RO water .... I'm thinking its magnesium deficiency somehow.... It's yellowing between the veins but they are staying green and it's only that last set of fan leaves rest of the plant looks normal . I water prob 3 lt between 5 plants every 3 days or so (they R in 7gal pots that i drilled holes in the bottom for drainage) I see some run off but I've noticed that the 707 does not drain very well... I water when the soil is dry knuckle deep not super dry just not that moist feeling and The pots feel light

I just calibrated my ph meter idk the ph or ppm of run off as of right now I just fed them yesterday .... Never measured it only before I put it in. My meter is acting a little strange even after i just calibrated I got 3 different reading from my water first it was 5.8 then I turned the meter off and back on then it climbed to 6.1then I turned it off removed it turned it back on and put it back into the water and it climbed to 6.3. So I did it again and stayed at 6.3 I mean this is rifht after I calibrated it and rinsed and dried it after so no solution was stuck on the end. Maybe I'm locking it out due to ph meter? I know magnesium locks out of soul at just under 6.5

I'll post a pic of the plant in the am before I leave for work ...

MattMA said:

Maybe I'm locking it out due to ph meter? I know magnesium locks out of soul at just under 6.5

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Phing nutrients poured into soil isn't that critical. The soil has more buffers to pull the nutrient solution than the nutrient solution has to pull the soil. If you fed at 5.0-5.5 repeatedly it would pull the soil lower. But, being 0.5 off isn't bad, IMO. It may depend on how much dolomite is in the soil.

Usually acidic soil is caused by overfeeding and/or no runoff when feeding. The salts build up.

For me, when the runoff is below 5.4, I'm entering the territory of lockout. The runoff ppm will be about 2500 at this point. For you it may be different. Also, it's not as accurate to do a measurement as a reaction to a problem. Better to track runoff ph and ppm from the start and watch for a trend. If you saw it go from 6.2 to 5.4, you'd know something's happening. (If you saw runoff ppm go from 1000 to 2500, you'd know you have salt buildup.). But, once you have a soil and nutrient worked out you don't need to measure this stuff. It's a waste of time. But, informative while working it out.

Ya def a really good point to keep a lot... That 707 has such shitty drainage I feel like to get enough run off to be able to pour it into something and measure it I would have to severely over water my plants if I use it again I am def gonna add a good amount of perlite to it

So those yellow leaves are like 70% yellow and the ends are withered I just heavilily watered the worst and fastest hanging one and measures the ppm coming (mind u I watered w 2ml per lt or cal mag in the water around 200ppm or so) came out 624 last time u watered I fed and I usually feed around 500 ppm or so .... 624 wouldn't constitute a salt buildup would it??? The pics online of leaves w salt buildup prob in soil looked right to me it's weird

Run off ph @ 6.7

I had this same type problem in an old soil i used. Would say you might have a nitrogen toxicity issue. Try flushing and re-apply some fresh new soil to buffer. Sounds like Roots soil broke down too fast and locked you up.

MattMA said:

So those yellow leaves are like 70% yellow and the ends are withered

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The plants look good to me. You're focusing on the lowest couple leaves. It's normal for them to yellow and die off. I don't see N tox, but I could be wrong. The leaves don't look glossy and your runoff ph/ppm isn't wild (two things you'd expect if overfeeding, which is how N tox happens unless you're feeding something really imbalanced toward N.).

I would leave it alone, keep feeding normally. If you start changing things trying to improve the lower leaves you may start a problem.