I've been breeding rats for some years now. I've only come across this sort of problem about 3 times due to the mother rat being a horrible breeder and mother all around or she was just a nutcase to begin with. Those rats do not late long with me since I will not have "bad blood" in my rat colony. I do 1.3 and rotate the females to give them time off. I also feed Harlan Tek lab blocked that are the 18%. All of my rats are handled from when they are babies and I make it a must to have every one of those rats respect. Nothing worse then having a mother rat chomp down on you when you are trying to spot clean her cage. Also I do switch blood lines up about every 6-8 months I'll add in another male or a few females and retire some of my old breeders. I too try not to inbred them since that only causes issues down the road.