This morning I turn up at the coop and find one of the 7 week olds look lethargic. He just finds the nearest corner and stands there with his feathers puffed up and doing nothing. A bit of back story that might help... at around 4 weeks I let them out of their nursery. A week later the hen lost interest in her chicks and they've been on their own since (the mother of this hen doesn't get broody, maybe that's something to do with it?). The chicks have been fine for all that time, though I did notice recently that this chick looks cold in the mornings with his feathers puffed up, not all of his feathers have developed, unlike the other chick who seems perfectly fine. By the evenings the chick seems better again. But now he's really lethargic. I've taken him and the other chick and put them in a cage, to avoid the rest of the flock attacking the "weakling". What possible problems could make it lethargic, and could it have anything to do with the hen abandoning them that early?