Just what everyone else said you'll need more cfls as side lighting or stand up
fluorescent tubing. The
hps lights are hot and you will need to vent all that heat away from your box. But the cfls can produce great fruit . ..the two yellow leafs are called ....erm ...i forget? (congtigons) ??? But they act as food for the young seedlings......its natural for them to yellow and die off
Happy growing.....have a look into getting some good bacteria ( bennies ) for your water .....there good for roots and
nutrient uptake and eat all the old dead organic stuff in your water and bad bacteria. Good luck