This is copied and pasted from my tread, but might help you too:

Best I can tell it's a zinc deficiency caused by high pH.

I watered mine with plain water with a pH of 5.5, the water seeping through came out to the low 6's.

It's been 36 hours and it seems like it's getting better.
Dorje113 Reviewed by Dorje113 on . Yellow leaves, spots - First grow - White Russian - CFL I did some googling prior to this, but honestly I can't nail it down. I beleive the issue started after last feeding (4 days ago). This White Russian is a clone I gotten a month prior. Its transplanted into soil 16 days ago. While it went well it took a few days for yellowing to disappear. About 3 days ago it showed up again. At first it started in middle (I think) and only effected the lower and middle leaves. One is yellow, probably canary yellow, and some dark almost red spoting on edges Rating: 5