That lamp is nuts man.

I think one thing with the 45W CFL is that with it being so close, the intensity might be too high to run is 18/6. If you're going to stick with a 12x12 screen, you're going to have a little bit of a difficult time lighting it evenly with only one lamp. Switching to 2 lamps of a slightly lower wattage might help.

I think based on your feeding schedule that you posted, you're probably more in line for 6 cubes/day. So I think the problem is two-fold, the light is too close/intense and your screen is oversized.

If you trimmed the screen down to 6" or maybe 8" wide and then tried to back off the lamps to about 1/2" from the reflector, and wrapped it to fit the screen, you would probably get better results. Also you would probably be able to cut down the light hours. I would say 14 on max, but until you start getting green growth, I wouldn't mess with that [i[too[/i] much. What you want is green but if you get yellow rubbery growth, then start knocking the photoperiod down 1 hour per week until you get a consistent green growth. If you get brown slime on top of green, then you're really close, just a bit too much light still. At least that the trend I am starting to notice.