Yes-it is very normal for the mother of the babies to go away from the babies and rest...this is usually when I see my other female or my male go and "sit" with the babies to keep them warm. They will all be fine-especially if you see little white milk filled bellies on the babies. You may have one or two that dies-almost always happens with mine-mice and rats...Just relax and they will be just fine. Keep a watch on them for any warning signs that any of them are stressed-but otherwise you are doing great!
Wendi