I've only ever had two babies that were furred eaten, they were both 17 days old and I promptly removed the rest of the litter and didn't breed from that female again, that females sisters proved to be abismal mothers too, and it was a very, very tough decision to remove them from my breeding program as they were the best typed does I had at that time.
I've had first time moms eat a few newborn pinkies, and a couple of completely desimated newborn litters, but I see that as run of the mill, and usually give the girls a second chance.
I hope the rest of your argente litter does well with the nanny Sarah!
W xx