Yellow leaves help

[Erbs2go]

I have only been growing for a year or so, and each time gets better and better. But my latest grow has started going yellow. I am using hydroponic dwc, with nutrients, the plants are a couple of weeks old and just started to change colour. The PH is kept within limits. While the plants are small I am only using the one 600w light at its highest.
Any help appreciated.

[CrudeMofo]

I'm kind of a noob but from what I see you have a pretty cute set up, the yellowing leaves is probably a nutrient deficiency of nitrogen. Get da nutes man.