We have a small flock of hens, 2 golden sex links, 2 amber whites, 1 barred rock, 1 silverlaced wyandotte, 1 americuana, 1 buff orpington and 1 duck. Two days ago we heard one of the golden sex links sneeze a few times. We had just let them out to run around the yard in the morning and she ran out with the rest of them. Wasn't acting any differently and she went with the others back into the coop at dark. The next morning I went to let them out and she was lying dead on the floor of the coop. I don't have a clue what happened! We got some powdered antibiotic for respiratory diseases at the feed store that you mix into their water and are giving the rest of the flock that for 10 days but I just don't know what killed her. Other than hearing her sneeze she seemed healthy. My poor little Hazel, I feel bad that I didn't even realize that she was ill.