Nest box temps

It seems like it is a problem from one extreme to another. I was concerned about the freezing temps a couple nights ago. The kits, born 4 nights ago, seemed to do fine through that because they had a very warm nest. Now it is 80 degrees outside. I had 2 kits pass, though I don't think it was heat related but I cleaned out the nest box because of that finding. So as I was placing the materials back and replacing some of the materials, i starting thinking surely these kits are too hot in here now. My question is, how much should I interfere with the state of the nest, should the kits stay covered in the fur if it gets over certain temp? The remaining 4 kits are really healthy, fat and moving around a lot when I messed with the nest. I just don't want them to overheat. I never even thought of that being a concern, but I live in a place where it is cold one day, hot one day. Fluctuates a lot.thanks for any advice from more experienced folks.

My mamma does will cover and uncover the kits with the pulled fur as needed based on temperature. I let them do their thing.