Bunnylady
Herd Master
Baby rabbits have trouble regulating their body temps until they get properly furred out, which is why it is critical that they have a good nest of hay and fur to snuggle together in. Babies that get separated from each other may be a bit cooler than their huddled-together siblings at these temps, but they shouldn't feel cold. Are you sure they are all getting fed? I would be very concerned about any that are noticeably cold to the touch, particularly if their tummies aren't full and round. Baby rabbits can survive without food for a day or two, but not much longer than that.