no offense but this isnt true about the cups. I go straight from germination to 18oz plastic party cups, 4 weeks veg under CFL's, then 3 gallon containers for flowering to the end. Never had a problem, but i wouldnt go any longer than 4 weeks MAXif u have leafs out u need somthing bigger than a plastic cup. the yellowing could be for nutrents burn, or lighting burn