My rats are mutts that I bought from pet stores--some from a store that breeds feeder rats, and some from PetCo or Petsmart.

I keep them in Freedom Breeder racks.
They were on lab block, but I have switched them to Doggie Bag brand dog food. I noticed no decline in productivity or survivability since switching (over 6 months now).
I tried adding in some cattle range cube for balance, but the rodents don't appear to like it as well, and they appeared to lose some condition on it, so I'm going to quit using it.

I have rexes, double-rexes, beige, hooded and solid in a variety of colors, color-point (love these), dumbos, and a bunch of other random stuff I don't know the name of. I hold back the rats that appear healthy and look cool. I have found albinos aren't my favorites for temperament or productivity. Beyond that, everyone's doing great.

I would say, if you're having bad luck with breeding rats, and your temps, your bedding, and the feed are all pretty much the same as what others are using...
You got bad foundation stock. Feed them off, and get new ones from somewhere else.