I agree with Amberlops - give her another chance and then replace her if the same thing happens. Here are some questions that were not addressed. Did the doe pull enough fur to keep the babies warm? Does only nurse at night so if the kits' tummies are plump in the am they are feeding. Was the nest box dry inside? If the nest box is in the wrong place (in the spot the doe usually potties), the doe will sometimes pee in the box. This will contaminate and kill the kits. Did you check all the kits after they were born for any dead ones left in the box? This can also contaminate the kits and cause them to die. Was there a hot spell - heat is worse for kits than cold. Did you have predators, raccoons, possums, rats in the barn? That can upset the mother and she will jump in and out of the nest box, trampling her litter. Finally, some does are just not good mothers and you should replace her if she is not able to successfully raise a litter.