Need help identifying leaf problem

[Scrizzly]

Hi everyone,
One of my plants started showing signs of some sort of problem yesterday. I was thinking it was heat stress so I raised the light a bit. But this morning when I checked on her it’s seems to have gotten a bit worse.

It’s the only one out of my plants that seems to be doing this. It is the tallest plant and the one closest to the light so part of me still thinks it’s heat or light stress.

I ph my water to as close to 6.3. I use general Hydroponics flora series and use around 35-40% of there recommended amount. I use CalMag at around 80% strength.
Temperature during day sits at 78-79 degrees and around 63-66 at night.

I have also noticed that this plant has slowed growing. This plant actually used to be my biggest plant but now is one of the smallest. It’s the highest because branches aren’t long enough to do LST and all the other ones are tied down. But even still with the other ones tied down there is only maybe a few inches in height difference.

Any idea what this may be?
It may go away from me raising the light but I want to get ahead of it if I can. This is my first grow.

 

[Chris Scorpio]

Dirt or coco

Looks like Mag issues

I've always run my calmag, when I use it, at 100% strength like all my additives, but yer good on the GH %, don't change that

Up yer calmag to about 150% for a week or so, then back to 100% , should help

 

[Scrizzly]

Thank you. I will give it some more CalMag when I do today’s feeding and see if that helps.
Also I use HP Promix mycorrhizae. I believe it is a Soil and Coco mix

 

[Virgin Ground]

pH should be lower for pro mix, I believe. Pro mix is considered soil-less.

 

[Scrizzly]

pH should be lower for pro mix, I believe. Pro mix is considered soil-less.

I didn’t actually realize it was soilless. I’ve been phing to 6.3 this whole cycle. That would explain some issues I’ve had! I’m reading up on it now and I’m supposed to be treating it like Hydroponics.

I wish I seen this earlier as I litterally just fed and watered the girls!

Next water I’ll try a lower PH. I’m going to look into it a bit more before hand just to confirm.

Does anyone have any experience with HP Promix mycorrhizae? What do you PH too?