You must be new to keeping chickens. Two nesting boxes is more than enough for three or four hens, it is actually enough for up to 6 or 7 chickens. Most hens share the same nesting box, they like to lay their eggs most of the time in a nesting box where other hens have laid their eggs. I had four nesting boxes for 12 hens and they never used more than 3 of them.
They made it. I through a big outdoor double cushion over the whole thing and checked on them and they weren't even bunched up for heat. It was quite toasty in there. Much warmer night now.
