I'm wondering what I am doing wrong. The mother, who is two years old, was in the great condition for giving babies. But, the babies started dying when they were 1 week old. The litter was 3 kits, and so far none have died yet, but it is coming close to one dying. 

*Note: This is only the second litter she's had.*

The place where she gave her babies was about 70 degrees Fahrenheit, in a barn, and the place where she gave her babies was clean. Should we turn up the heat in the place or do something else?

We are feeding her rabbit food pellets that look like a brown tube which was recommended food by the store we bought it from. She went to the vet 2 days before she was going to have her kits and everything was good.