One of my pullets this year has stopped growing and feels skinny and light. Compared to her sisters she's pretty small and I'm not sure what's wrong. She enjoys food and has no other symptoms that I can see. I lost one of her sisters about a month ago to unknown causes, and one of my bantams in the coop next door to something similar (got very skinny, died of unknown causes). I've treated with Corid and that wasn't it. Could it be worms? Something else? I have no idea. Any ideas?