Yet another plant problem

Any ideas?

Straight coco w/ 1" gravel in bottom

3 gallon bucket hand watered once daily w/25% runoff

H&G nutes at 500 PPM

PH = 5.9

Lemon Kush from seed 7 weeks old.

Seems like it comes and goes but only on older fan leafs. top growth is perfect.

400W halide 18" above canopy

RH 47% and temp is 65F night / 78F day

City water at 70 PPM base.
Any guesses. T

i can't say for sure, but my plants do the same thing. i think it could be light not getting to them.

pH is on the high side.

as always, for best resluts fill out the T/S form....lol!


-shake