Can’t figure out this leaf problem

Not sure if it’s a potassium deficiency or something worse. I’ve never dealt with bud rot or mold so idk where to start. I was only giving these girls in later veg about 800 ppm (half recommended) and am gonna boost it now.
my PH fluctuates between 6.2-6.5
Using promix and heavy 16 nutes with growers choice lights at 50%. Smart pots, plenty of air circulation and not a bug in sight

It just looks like you let your plants get big without enough food
I would make a foliar spray of a nitrogen rich product and soak it down after lights are off

agreed looks to be a nut. issue

Probably low pH from peats natural acidity when breaking down. I feed higher pH of about 7.5 to combat this. Some guys like to use "Calmag" as a buffer in mid flower.

I personally use silicate but still need to run higher pH than what I plan on feeding the plants in peat based mixes. Cheers!

If I check the run off PH it should be close to what I put in right?