I had this happen once, and discovered that the bedding I had bought was full of mites! I pulled it all out, treated the area and the girls, and replaced with new bedding. They roosted back in the coop immediately.Well, I only put the light in days AFTER they started this. It’s just a small string of Christmas type lights. I thought they’d like that for the 2 hours at dusk. Since it didn’t work I kept them off the past few nights. Occasionally one or two will go in but the other 4-5 huddle outside. It’s brighter outside than in the coop. Thanks for reply!!