I have the exact same Problem But mine dont look that ruff. At one point I believed it was bugs eating the tops of my leafs (I saw small Larva style bugs yellow and orangish colour) then the leafs dying slowly under the light. But I only saw the bug on one plant that I had brownish leafs and now most plants have browing leaves. I will post some picture tonight.

I think its a Heat issue. It can get pretty hot in my Cab and Its almost as if I see the leaf satrt Green then slowly look like it fades in colour then after a week it gets brittle and brown.

Maybe its a nute Burn, I feed then a little nutes at 3 weeks old 1/4 strength and watered down from that too. Botaincare Pro Grow. But the top leafs are nice and healthy so I dont think its nutes.

I tested my Ph Runoff water and It sits around 5 - 6 I think that is ok. I use ProMix BX so Its balanced etc.

I think its heat cuz the leafs stand up on the tip edges and I read that if they stand up they are protecing themselfs from Heat. but The very tips of some of my leafs curl down. Not sure what that means yet still searching./

Will post some pictures later. Hope we get this one figured out

kdspecial