What to do with stupid breeders

[Batdad]

I have 5 colonies of rats I am breeding (1:2). One colony seems to be remarkably stupid or something. They have had a couple of litters now and all they do is bury them and forget them. I have seen the burying thing before, but mommy always goes back and takes care of them. While cleaning yesterday I found five dead pups and five live one, barely. I put them in with another mother who had only five last litter, although the original five are bigger these new guys probably stand a better chance than with the original parents. Question is should I try splitting this colony and putting them each with a good mom or turn them into lunch?

Thanks for help
Bruce