We have 10 3.5 week olds. A weeks ago separated them into two brooders for more space. (Not a laundry basket, this was for containing while I clean) This morning this one has bloody tail feathers. Is one of the others pulling them out? What do I do?
They are pecking at her which can turn to full out cannibalism and death for her. Blu Kote for the pecked bird and more space for all of them. Good luck.
Those birds are old enough to be out in a coop/run full time without heat. Keeping them inside in tight quarters where they can't engage in normal chicken behavior is a recipe for all sorts of aggressive behaviors leading up to blood shed and cannibalism.
Spray the wounded area with Vetericyn and then apply Blu-Kote (Wear gloves for blu-kote because it stains really bad!). An additional step would be to find Rooster Booster; Pick-No-More lotion.