PLZ HELP, plants starting to die on me!!

6 weeks old
20cm high
new branches just forming out of main stem
2 X 100W CFL
feed them potash, and a phosphorus mixture


The lower sets of leaves are all turning yellow and dropping off, the round ones, and then the first 4 sets have all turned ellow and dropped off, and the next 2 are beginning to yellow, what do?

this was beginning before i started to feed them, and i havent noticed any change since feeding

also i dont have a ventilation fan or anything, their in a cpboard in my room, and the most ventilation they get is me opning the door for a few mins a day constant 25-30degrees

need pics perhaps its pot size try moving it to a bigger pot

here you go, its the one on the bottom right its in a 2l container probs liek half filled wit dirt, u can see sum of the falen leave son the gorund in the pic and the next 2 begining to yellow

put holes in side of container at ground level, put something under to let water out, air in

bigger pot

yeah man defo bigger pot