My 6 chicks are in their new 4x6 coop open to a 10x6 run. Today they turned 5 weeks. I have a light bulb still in the coop because it was dipping into 50's at night. They are free to go inside to eat and drink but they spend the majority of the time in the run. When the sun goes down they won't go in the coop they lay in a pile freezing. I have to catch them and lock them in. I thought they would go in at night abd u could just go out and close the door. Are they just too young? Will they catch on?