OH! I am so sorry. I agree it must have been the cold. I was worried about that when I put mine out at first. They were the same age as yours. I would hold my breath every morning for the first week when it came time to open the door! It was still getting down to the 20s here at night. We did add a space heater as well as the heat lamp. It is still only in the 30s at night so we are still using the heat to hold a good temp. Our big girls prob don't need it now but we added 10 more babies to our flock!
HELP!! I CAN"T STOP!!!