Some updated stats and pics would be good for a proper diagnosis

SMG

From what you're describing to me, it sounds like a N deficiency, but that could be that your pH is possibly messed up. Hit us back with detailed stats and some pics and we'll see what we can do.
SauceeMcGee Reviewed by SauceeMcGee on . Leaves On My Plant Are Almost ALL Beginning To turn Yellow I'm AFRAID It's Gonna Die! Well I'm a "FIRST/SECOND Timer" Before now I have only grown small plants from seed and sold them at about one month old... Your Equipment: .1) Type and wattage of lights: OUTDOOR. .2) Distance From Tops: N/A .3) Reflector type? N/A .4) Is there a consistent fresh air supply? YES, definatly Rating: 5