Yep, sativa's are sensitive to N, and the incoming PH is too low. Is it possibly time to repot? Lockout with burn.

Flush and repot if you can and lay off the nutes. Use molasses 1 tsp/gal
WashougalWonder Reviewed by WashougalWonder on . Help Please!: Not Sure What is Wrong... Has anyone ever come across this problem? The leaves are turning yellow, near the bottom with some brownish colors and I can't figure it out. Here are some pictures: Rating: 5