idk what that other guy is talking about but i would recommend looking into getting a handful of cfl's
for overhead lighting and use the t-12's for side lighting..
you are going to be looking at using 10-15 bulbs
if you seek any kinda bud density you need 5000+ lumens/sq ft..
you REALLY dont wanna turn em back to 24 hr unless you HAVE TO!!
this will cause hermie and WILL NOT LET THE PLANTS MATURE CORRECTLY!!

if you are curious about what CAN be done look around for grow logs and
READ them before asking these questions..
they have been asked many times and you will only irritate most members here

to recap get CFL's and a bunch..
get rid of any of your plants that look weak
keep a COUPLE good ones in flower and
CONCENTRATE the light you DO have and any you might get
on the selected couple

thats the best i can do for now hit up one of my logs if you
take some or all of my advice and we can go from there

~MG