Strange leaf discolouration/patterns. Please help.

[BalzarDanglin]

Hi all.

The last couple of grows I've had the same issue pop up, and I can't seem to get to the bottom of it. I'm hoping you lovely people might at least be able to point me in the right direction.

I'm growing autos, specifically Speedrun Granite Haze F6, Terp Sneeze, and Acid Snow. BUt have had the issue with Mephisto genetics as well.

Strain: Speedrun Seeds Granite Haze F6
Soil: Cre lightmix (it's an Irish brand and IMO far superior to Biobizz)
Nutrients: Bhudda's Tree Organicus (had fantastic results in the past with it). I was using a small amount of Biobizz calmag (0.2-0.3ml/L) but have cut it out as I saw no improvement and didn't want to throw things off further.
Light: Migro Aray 4.
DLI: ~30 at week 5. I've been playing it safe worried the issue could be caused by the light being too intense.
Light schedule: 20/4
pH: Fluctuates between 6.3 and 6.7 from measuring runoff. I caught it once over 7 (nutrients in the base were unstable) but removed the water from the base immediately.
Temp: 78-79 lights on; 74 lights off
VPD: Currently 1.0 to 1.1 (managed by controller and humidifier)

They sit on ACI self watering bases. I had fed once through the base, but now only top feed.

I was feeding every watering, about 2ml/L of Organicus (recommended dosage is 2-4ml/L).

I start in solo cups then transplant to final pot (16L/4G). Everything goes well up to that point and for a while after that. Then this strange discolouration starts to appear, where the tips of the leaves become a mottled yellow/light green.

First signs were an overall lightening of leaves, which I took to mean I needed to start feeding as I hadn't fed to that point (~3 weeks from sprout). Feeding has done nothing.

I then switched to assuming it was a pH issue, but pH has now been quite steady between 6.3 and 6.7 over the last 2 weeks. I allow for a bit of a range to make sure the plant has a chance to unlock the different elements available at different pH levels.

I hate to be that guy, but does anyone have the foggiest idea of what might be happening here? And how can I combat it?

Is there a trick to keeping pH steady? I leave water out to denature and use that. pHing as needed. Tap water is ~25ppm, quite pure, but low in Ca and Mg.

Am I watering wrong?

Any help is very much appreciated.

Thank you all!

 

[Cozychronic]

Im no expert, but looks like variegation. Genetic

 

[Cannaficionado]

Now what kind of medium is yours? Peat or coco based?

It doesnt really look like any kind of deficiency or lock out Ive experienced. Normally with something like this you'd expect maybe sulphur or magnesium but normally it doesn't appear in such fine dots. It could be though, your ph seems fine and you really don't gain any info measuring run off in a peat based medium.

Its an expensive option but apera makes a ph probe specifically made for measuring soil ph. Its a long pointed probe and its usually about 20-30 bucks more expensive than their basic ph60 probe, but the probes are replaceable. 20 bucks whenever the probe starts to fail.

Im leaning towards the above. Variegation could be what you're seeing, which is a natural color shift in the leaves. Could be yellow or a different shade of green, but the tissue looks healthy and if its not dry and crispy I think this is more of what you might be experiencing.

 

[BII]

Could it be a plant pathogen, particularly a virus infection?

 

[Cannaficionado]

Now what kind of medium is yours? Peat or coco based?

It doesnt really look like any kind of deficiency or lock out Ive experienced. Normally with something like this you'd expect maybe sulphur or magnesium but normally it doesn't appear in such fine dots. It could be though, your ph seems fine and you really don't gain any info measuring run off in a peat based medium.

Its an expensive option but apera makes a ph probe specifically made for measuring soil ph. Its a long pointed probe and its usually about 20-30 bucks more expensive than their basic ph60 probe, but the probes are replaceable. 20 bucks whenever the probe starts to fail.

Im leaning towards the above. Variegation could be what you're seeing, which is a natural color shift in the leaves. Could be yellow or a different shade of green, but the tissue looks healthy and if its not dry and crispy I think this is more of what you might be experiencing.

You know I didn't see it before but your lower leaves look like they are showing signs of potassium toxicity. The edges are brown and dead. It is possible that this lead to a snowball effect, altered the ph of your root zone and locked out pretty much all of your secondary nutes like calcium and magnesium, when that starts to happen its like slow falling dominoes because those build up and start effecting uptake of other nutrients. Try watering with plain ph'd water till the lower leaves show signs of being generally hungry, a little pale, droopy and give them like half or 3/4 strength feeds until they show signs of bouncing back. It may take a while but your plants should still flower out and be harvestable. Ive been in much worse spots.

 

[Drownomatic]

Potassium lockout from some other excess salt.

Too much Posassium causes new upper leaves to be needle thin.