MrsWC...looks like water stress to me...meaning the grow medium is overwatered leading to fungus and algea growing in your medium...what medium are you using...also, what method of growing are you using...from your pics, i think it's dwc? Also, very important is Ph...you want an optimal ph of 5.5 in dwc with it being ok to be between 5.2-5.8....looks mostly like water stress to me tho...2 inches below netpot should be ok....make sure your airstones are functioning correctly...check my thread for help on dwc and recirculating dwc setups...it may help you with some ideas.
http://boards.cannabis.com/showthread.php?t=50769
-sD