We have had chickens on and off for years and decided to get some more this year. We have started to hatch out our own. We have been doing really well with them all except for the last week. One of our pen that have 15 - 6 week old chicks in it we noticed that they were losing their tail feathers. Like they were being ate down to their bottom. And this morning there was one dead. And when we inspected it his bottom looked like it was hollowed out. All the other birds looked alright except for the tail feathers. Went out for our 3rd water/feeding and found another one dead, and it looks the same as the other one. I've been searching on line for some help but haven't found anything. Thought maybe lice/mites or fly-strike but no evidence of that that I can see on the dead or live ones. Then thought they were picking on each other, but I sat out there for 30 min. and didn't see any sings of that. If you have any ideas please help, I just don't know what to do. Thanks so very much!!