I don't think it's the light. The lights are over 2 4x8 beds. 2 lights per bed and the lights are up high until they are better able to handle the heat. My set up is exactly what someone else I know is doing and they usually come out with 6lbs, but they have not ever ran into this problem before. I have and 8in exhaust and 6in inlet, with 1 to 2 fans going. Temp stays around 83-85 degrees and humdity is around 30%. I do think ph may be a problem. Thanks for the info everything helps.