We have a four week old barred rock that I found this morning just laying with it's head tucked into her chest. We have 25 total in a brooder with seemingly adequate space. When I picked her up to examine her, she has no wounds. Her neck feels fine. And her legs, feet, and wings move freely. It's just that she won't lift her head. When I bring her head out slowly to she her the food and water, she doesn't take it. This is very sudden. Last night everyone seemed normal. We feed them the normal Blue Seal medicated chick starter. We have isolated her for the moment and are going to do a complete fresh bedding change. We'll post pictures in a moment.