I think this looks like a magnesium deficiency. Add a teaspoon of Epsom salt per 5 gallon to your nutrient solution.
(This will only affect new leaves!)

Will do. I have epsom salt on my grocery list.

I think im siding with greystoke on that one. I work at the garden cent at my local lowes. We have to learn all about plants and nutrient deficiancies if that doesn't work try adding some "ash" to your mixture. Anythin kind of ash like from your charcoal grill or a wood fire. It's really good for the leaf develpment.