It's part of the clutch of chicks I hatched from fertilized eggs. The other six, at 2 1/2 weeks, are bulking up and doing fine. This baby started showing up as undersized as of last week, and chirps a lot. Unless it's being held, it's chirping most the time, which I take as a sign of distress. The chicks were brooded by hens and go into the run to forage, now. It trails behind the others and has a more huddled posture. Often, it's separate from the main bulk of the chicks and seems to be breathing through its mouth a lot of the time. After watching this in chillier temperatures, and feeling there was something wrong, I took it inside. It's now in the bathtub with a heating pad, food, and water. It has stopped the incessant chirping, but still isn't terribly active. It seems to be eating, drinking, and pooping normally. I put a little sugar and apple cider vinegar in the water, and am hoping to either have it recover or see if there is something more I can do, maybe learn something from you folks. Or wait for death, since I really don't have the foggiest idea of what's wrong. The warmth seems to help, though. Any thoughts or suggestions.