Week 1 = 95 degrees at the warmest part.
Week 2 = 90 degrees at the warmest part.
Week 3 = 85 degrees at the warmest part.
Week 4 = 80 degrees at the warmest part.
And so on....
First, I'd get them on a better feed, that is nutritionally balanced for their needs. Source it from a feed store, not a pet store. What bedding are you using? Beware of cedar shavings, or chips.
When you say "good" temps, do you have a thermometer almost at floor level to measure the temp...