Unusual leaf problem

[The Iconoclast]

I've not seen anything like this before. This is in an aeroponic set up using GH nutrients. Everything should be good, the roots are nice and white and healthy looking. It's just over two weeks old and as you can see the leaves appear to be dying and it was looking strange from an early age. I don't think it's just the age of the leaves. Lights were at about 12 inches when it was younger but then I only had 50W of white light from a viparspectr700 so it shouldn't have been bleach, it's at 24" right now with 100%W 10%R and 50%Blue

It's an OG Kush auto, temp and humidity are all good. Does it look like I should be concerned at this stage.

 

[Banjacked]

You mention temps and humidity, what's your pH?

 

[The Iconoclast]

Oh yeah, pH is around 6. Here's another shot...

They were on about 500ppm, I added a tiny bit more of GH micro and GH grow to get a bit more nitrogen in, which took it up to 900 I usually like to keep the nutrient a little on the low side until another week but I thought I'd see what upping it a bit now would do. After a day it is not worse or better. 900 is high but not high enough to do any damage. It still seems to be growing fine. That brown bit on the end of the leaf is soft not dry.

 

[The Iconoclast]

Here's a couple more shots where you can see some of the pale edges on the higher leaves. I'm at a complete loss to explain this :¬(

btw, this is the plant in my current grow journal https://www.autoflower.org/threads/first-auto-after-22-year-break.67641/

 

[Waira]

in hydro, pH is very touchy,..how are you testing it? if it's not a well maintaned meter, it's not a reliable measure,... keep in mind, the pH scale is a logarithmic one, meaning each full point (+/-1.0) is in fact a 10-fold difference,.. decimals matter here big time,... have a look at this chart, and you'll see why a small drift or inaccuracy in pH can cause defc. problems,... Id say from the looks of those symptoms you're having a couple things happening,.. yellowing tips look like a K issue, and new growth paling out is an early micronutrient defc. starting,.. hard to say which yet,....

 

[GoAuto6]

I was also gonna add with hydro needing to be on point a pH meter and good tds are a necessity, strips can give you trouble.

 

[The Iconoclast]

OK thanks.

I have a cheap Ph meter which I calibrated when I got it with the calibration powder. I have ordered some more calibration packets so I can check the calibration.


According to my pH dropper solution which is yellow at most maybe even a tiny bit orange, would indicate around 5.8

My pH meter is indicating 6.3 which should still be OK.

So you guys seem to be suggesting some sort of nutrient lock up rather than some sort of light bleaching?

I have attached another photo. I removed one of the lower leaves to give it a more thorough examination under daylight. The problem is much easier to discern now. I'll report back when I get a new calibration. I've marked a mark in red but I see now that these marks are not the same thing.

I've just discovered there's a bit more to this pH business than I knew. Apparently pH and alkalinity are not the same thing. I've decided to trust the meter until my calibration solution arrives in a few days. I've moved the pH down to 5.8 according to the meter which is 5 according to the indicator solution.

@Waira, I'm using the GH Micro and GH Grow, so I'm hoping I'm properly covered with the micro nutrients and the grow as extra K too, so the potassium should be good, with the PPM at 800 now. I'll see how it goes and report back in a few days or so. Meanwhile the stem is getting very strong and the roots are looking good. So hopefully it is just the pH causing the nutrient deficiency.

 

[GoAuto6]

5.5 is usually optimum, and my experience with hydro was even when I'd get out a couple points it went bad fast..

 

[Waira]

.... good on the meter calibration, and the ppm's look okay for now,... look for halting of symptom progression, the other damage isn't reversible,...

 

[The Iconoclast]

look for halting of symptom progression, the other damage isn't reversible,...

Hey thanks. I've only just started to feel good about this after a tense few weeks. But I'm into day 21 now topped at fourth node and removed first node shoots, (not sure if that was a good idea or not) So there's now 6 shoots trying to poke out. The plant is ridiculously stocky and about 4 1/2" high. I'm back down to about 700 on the nutes and I'll prolly keep it around that the whole grow. Newest leaves have no damage. You can see how it's doing in my sig!