It could just be first time mom issues. Hopefully they do better next time. If not, I would cull them.
Pairing new moms with an experienced mother will help. Especially if that experienced mother has a litter at the same time too.

Hopefully your 3rd mama adopts your abandoned 9.
When putting in strange babies into a nest, you want them to try to smell like the mother's babies as much as possible. Rub them with some soiled pee bedding and it's best to integrate them into the mother's litter. She might foster them no matter what, but for the best chances, you want them to smell like her pups. I don't think they would have to compete much for milk. They rotate nursing times. I've had a female successfully suckle 20+ pups because the second mother in the tub basically decided to give herself a vacation.