Post pics of the brooder, the chicks, and their poop. Also post a list of what feed you use, any treats you give and any vitamins/supplements and medicine. Give your general location (state/province) and where the brooder is being kept.(house, barn, shed) Keep an eye on them and see if there's any changes in behavior ( lethargic, panting, sneezing etc) The more details you provide the better help you can get.