half hps, half cfl

So i have a young plant who gets 12 hours of hps, and then 12 hours of cfl while my flowers sleep. i cant think of any reason why, but it seems to grow slower than my 100% cfl grow. has any one done a half and half grow before?? im not worried, but just curious.

18 hours is all you need.I use cfl's for side lighting when I'm flowering.I also us um for cloning.Just make sure you don't break um,then you got a hazard.