I have four plants growing from clones. They are very healthy, but two of the plants have distinctly yellow edges on the fan leaves. No curling, blemishes, etc. I have now cut the lights to 12/12. I had a halogen light aimed at the two plants in question. I now cut that out, because I think it may have been too hot and caused the problem. (The two plants not in the bulb's rays are fine.) The plants look great, except for those edges. (Hurray for SB 420). 
