Help - variegated leaves

Old timer / first time growing. After searching previous post I believe I have an iron def. Thought I would ask the experts.
Planted 4/22/11 - Indoors - five gal buckets - have given no nuts other than worm castings in soil mixture & one feeding of bone/blood meal - 400 W met hal, 20 on 4 off - ph between 6 & 7 - water appx every other day.

thanks
DannyLee - Vietnam Vet

I might add - the color in the pics is a little vivid - actaully the yellow is more yellow and the green is less green. Six plants - 2 white russian at the top - 1 Barney LSD and and 1 Barney Vanilla Kush in the center - 2 white widow at the bottom. the 2 W.W. are the most affected with the yellowing - one of the W. R. having some light yellowing.