Four pullets, 13 weeks old, well-grown, very normal in all respects ... except they don't roost. They sleep in a heap in one corner of their coop, piled on top of each other. And it's NOT cold. 75 degrees at night. I don't recall this being an issue before. I raised four pullets last year in the same coop, they roosted ... well, pretty much as soon as I moved them into the coop from the brooder. Figured out the warm spot under the heat lamp and snuggled together under it (they still do snuggle together when they roost). These girls were sleeping all crowded into one nest box, so I put up a board over the boxes, thinking that would do the trick. But no. Any ideas, suggestions?