They are in our rabbit barn which 10x12 feet insulated shed. It is about 70 degrees in there during the day. An additional question she is still bleeding a little and she delivered her last about 14 hours ago is this normal?What is your setup, how warm is it now where you live?
Biggest problem for single kits is staying warm, if chilled digestion doesn't work properly. So insulating the nest/nestbox as good as possible is one way if it's ambient temperature is warm enough, or you can bring the nestbox inside and return it twice a day for feeding. Or bring both inside.
When I have winter litters I put an electric heating element (well, it's actually a misused electro magnet connected to a car battery charger with some fat capacitors to keep it from humming....) under one corner of the nestbox, kits will wiggle to their goldilocks zone.