We have some fully feathered banty cochin chicks. I'm not sure of the exact age, but somewhere between 9 and 11 weeks is my best guess. First one showed up with bare areas on the underside of their 'butt' and then a bare area on the bony top edge of the wings. He was hatched separately, solo, and raised with some chicks that were 2 weeks older. He looked poorly but was active and eating well, but suddenly died. Now, three other cochin chicks from a different hatch are showing feather loss, and one has died. Two have/had a 'bare butt' (underside only - the tail and upper backside feathering is normal) They also show poor feathering under the wings. One has a bare chest over the crop, though his/her rear end is normal. Both have necks that are kind of bare as well. One was found dead yesterday. He was probably dead some hours, and maybe a full day, since it was in a location we might not have noticed immediately. The dead one looked weird in that one side of keel had a lot of air under the skin, while the other side did not have any. On the side that was not swollen with air, it looked dark under the skin, towards the rear, where I guess the digestive tract would be. Kind of purplish and when I felt it, that section was also very hard to the touch. The dead chick had an empty crop, though food is available at all times. I checked the other chicks, both the normal looking ones and one of the bare-ish ones, and none had the air bloating. I think one of the bare ones may have the hardness towards the rear, but I'm not totally sure about that. The ones with bare spots feel hotter than the ones with normal feathering, but maybe that's due to needing to keep higher temps because of the feather loss? We have other chicks in the pen, slightly older, and other chicks in other pens. Only the cochin chicks have shown this problem. They are being fed a mix of chick feed, layer feed, scratch and greens/fruit/veggies as treats. They're in a pen with older chickens so if they choose to, they can have layer pellets. I never see them eating pellets, though. The de-feathered ones are active and eating, but since two have died already, I'm very worried about the others. We have hatched out a bunch of other chicks this season without problems, but these cochins, all from eggs from our cochin trio, have been a problem. The parents of these chicks were purchased this spring as adults and they look and act healthy. Other broody hens were used to raise the chicks. Below (if i did it right) is a photo of a problem chick next to a normal one. In the photo, the chick with the problem is smaller than the other, but that's just an coincidence. We happened to pick up the biggest of the chicks to show as our normal example. Anyone ever see this before? The weird air and hard 'organs' of the recent dead one freaked me out.