Really really yellow fan leaves! please help!?

Hi Guys im a new grower and have some cheese in there 3rd week of veg... they are in coco and im feeding in canna coco the stated measures... the temp is 24 lights on and 20 lights off...im using 600w lights, ive been giving 1/2 litre every 3 days to each plant and they are growing rapidly but tonight i have noticed they are going bright yellow. Ive had a read about on here and noticed that i have not watered without feed.... will that be my problem?
Would really appreciate some expert advise. cheers!

anybody???

If your using coco you are going to want to flush your medium every couple of feedings. the fertilizer salts will build up in the coco as the plant draws water out of the solution, this will also affect your PH so a flush as often as possible will prevent this. Sounds like thats whats going on in your case, salts building up affecting your PH and in turn locking out your nitrogen. When i used coco i used to feed and water every other time, worked out great. Good luck! I love growing in coco by the way, great medium.

Thanks for the advice figtree! you were right, ive flushed with water twice now and the green coming back through.... im gonna feed water feed water now on.! Turning over fri if there all backto normal... Cheers!!