I doubt your problem is heat stress from the cfl's, you can get a cfl within an inch of a plant and you won't get burnt leaves. Also if it was the lights, the tops would show the stress 1st and they would show it by forming a tiny upward "lip" around the edge of the leaf.

I agree with Gojira, one issue could be overwatering (droopy leaves). But I think the dried up leaves could be a different problem.

Are you adding calmag to your distilled water?