i was having a major problem with my babies, the lower leaves were drying up and died off, and all the plants were almost neon green. i started applying nutes, then the leaves turned lush green the next day. i think yellowing can be a sign of deficiency, how often should i water though? my babies are like 4-5inches tall..pots are arnd 25cm wide and arnd 25cm tall.Whoa whoa whoa, Hold your horses. Yellowing leaves is NOT a sign of Nitro def. It's a sign of overwatering or nute burn. Purple stem is a sign of Nitro def. Anywho your just overwatering your plants. Just relax your babies will grow use MG every other watering and you should do fine. DO NOT FLUSH. unless your plant has a REAL problem. Oh and if you HAVE to flush dont kill your plant by doing that. Just water your plants until you see the water coming out the bottom. And then water normally for the next two and your plants will be happy.
check this out it may help ya, has great pics and problems http://www.drugs-forum.com/growfaq/97.htm
kiss-ass