Egg yolks are the most complete source of essential amino acids and protein of any food. What I do is make scrambled eggs but instead of cow's milk (which is nutritionally inadequate for mice--or humans!) use human infant formula or breast milk. You can also mix in high-protein (~35%+) dry cat food, sunflower seeds, grains, and such with the eggs after they're cooked. I need my mice to be big for the show bench so I feed this to all pregnant and nursing females and still-growing young mice. I also cull the litters down to 5 or fewer per mother. Perhaps one of the mothers was eating a baby because they simply have too many? Fourteen (even between two mothers) may or may not be too many to handle for the individual mice. Good luck!