I have 7 week old chicks outside in a coop with an attached run. They are in there full time right now. Problem is, when it is dark they just huddle up in a corner and do not go into the coop. I did lock them up for a few days when they first went out there so they knew that was home. I have food and water in the run and the coop. What do i do to get them to go in on their own? I am going out of town overnight in a few weeks and i don't want them out in the run all night. Any suggestions??