My newzealand red doe had a litter of 6 kits. And they are supposed to be 4 weeks old now. About a week ago, I found one kit dead outside the nest box. I figured it was the cold night. A day after I found another one dead, also outside the nest box. Also I thought it was the cold night. Yesterday, I found 3 dead outside the nest box. With 1 kit remaining, I decided to take him inside my house for the night and during the day, I will put him back with the doe. Everything was fine, he ate grass, drank some water, he even pooped and urinated. This morning, I woke up finding him almost dead, he was breathing, but not responsive. His head was tilted back and he kicked when I picked him up. Just before he died, he let out a little noise. His belly was not swollen, so it could not have been bloating. The box I placed him in was wrapped in a blanket, so I cannot see how it could be the cold. Can someone please tell me what was wrong with him? And how to prevent it from happening in the future?