We're raising a mixed flock of meat birds and layers with ducks. They're all 4-5 weeks old Everyone is fine, up until yesterday. One of the meat birds was isolating, and totally unflappable when the coop was being cleaned. When I brought watermelon (we've had a heat wave) s/he didn't eat any. I brought the bird out to eat separately, which it did. Wondered at first if it was not getting it's share of electrolytes etc. what with the heat wave. Not the case as far as I can tell. It's isolating from the rest of the flock and sleeps a lot. Not doing much self care. Hand fed it egg yoke and fruit tonight, and initially ate enthusiastically, but ate much less than expected. Seems thin. No injuries, mites or abnormalities I can find, although it doesn't fold one wing in normally when lieing down. Any advice appreciated.