I have 7 pullets all together. They are egg layers and I've had them since they were chicks. Mornings ago I noticed one pullet did not leave the roost when I brought scraps out. Later I noticed it just hunched on floor of coop. This morning it was in a nesting box but this evening while six others were roosting it was sitting on floor. All seven were once laying but now only four with darker days and colder weather. I am thinking this is an infection from unclean and slightly crowded conditions. I will be disinfecting everything tomorrow. I never expected having 7 at this point. So I am weary of them all doing well together. Do I think this is an infection and treat with corid? Do I treat all of the chickens. I do not have a lot of options available but I want to do what is right for the chickens. Any thoughts would be greatly appreciated!!