It might be a potassium deficiency but not light burn (light burn curls the leaf edges up, especially on the new growth), have you been testing your solution and run off?
And potentially mag/cal deficiency too, point is though, it's the ph that's most probably wrong and now you see the consequences. Post your ppm/ec and ph if you can.
I grow in full organic super soil. I mix half ro and half filtered tap to get my tds to around 175 ish. I ph to 6.5-6.8
Why bring it up to 175 with the half filtered? I'm not familiar with super soils. Maybe there's an organic section on here on how to adjust accordingly?
Damn sun, that's some polluted water you got there, where'd you live? Any reason why you wouldn't just use full ro water?
Was using r/o at first but didnt wanna have to supplement cal mag so decided to go half and half plus saves some money
But then you're putting chloramine (and other nasties) in your plant which may have locked things out. Try giving it a couple of 6.0 ph waterings, as it could also be an iron deficiency if your ph is consistently above 6.5. Quite common.
Well two things. The filter i have removes chloramine but there isnt even any chloramine in my tap. Also i was giving 6.8 (according to my ph reader that needs calibration) For all waterings and they were fine. It actually happened when i lowered to what i thought was 6.5.
Ah yes I forget you have the special stuff, try posting your question here Growing Organic Marijuana They'll have a better idea of what to do, this section is for first time growers and there's not a lot of organic stuff going on.