I have 11 chickens. They are about 6 months old. They have been going to bed great till the last two nights. We have had a brooding light on for them. Last night 3 decided to stay out. I checked on them after the door closed. That is when I found them. I put them in. Tonight I decided not to have the brooding light on thinking they would go to bed at dusk just like this summer. I went out and found 7 of them did not go in to the coop. So of course I put them in but 3 of them came back out before the door closed for the night so I had to gather them up again and put them in. Why all of sudden are they having a problem with going in to their coop at bed time?