Have you thought of changin your water more often? 40-60ppm is a bit high for nitrates. Im not saying your fish are unhealthy....just saying that may help w/ the stability of your dats. Tank and stock looks great by the way.
I feed with the lights on as well but they will rarely eat. That is the only reason I feed with lights out most of the time because they all come out and wait in the front of the tank