It's my girls first night out. They are ~6 weeks old. I just went out to check on them (9:30 PM) and they are all huddled together in their run. I put a light in their coop hoping that when it got dark they would head inside. While it was still light out, Twiggy (the smallest, a BO) went up the ramp into the coop, but wouldn't go any further than the door. How do I get them to use their coop?