Hi there folks. I have 8 hens (mixed varieties), and I have moved them into their coop. When I moved them from the brooder to the coop, i kept them inside for two days, then opened the trap door to let them wander down the ramp into the run. Some go back in and some don't....and it is never the same ones! I always go outside about 30 minutes after dark and move them inside for the night....it is COLD at night here in the northwest. Suggestions?