Chick had to be put down, what could it be?

[zowieyellowflame]

I had a barred rock chick, about 5 weeks old that 3 days ago suddenly became weak. She stopped eating and drinking as far as I knew and was always fluffed up even though it is very hot out. When I picked her up I could hear a bit of conjestion in her breathing. Just a bit, no cough or sneeze. I fed her egg, which she devoured a few morsels but refused to drink water.
Then, the others tried to peck her to death while I was at work. She was suffering and not able to eat or drink so my husband put her down.
Just wondering what it sounds like? I do know I should have secluded her, I am sad I didn't, but too late now. They are on medicated feed.

 

[Hollywood Chickens]

I don't know what it could have been but I'm sorry to hear about your chick

 

[AngieChick]

I am so sorry this happened, I know that it can be very disheartening. At this point, I would look into a necropsy since the other chicks were exposed. There are just so many things that it could be that it would be very difficult to narrow down enough otherwise. Do keep an eye on your other chicks and isolate anyone with symptoms immediately.