i am new to chickens and have only had them for about six months. i got them from a friend who's dad owned them and passed away. he had alot of chickens in a fairly small pen. they had pecked eachother alot and kinda looked rough. i got them home and been doing everything i could think of for them. got their feathers back and look great now. but i had noticed about three weeks after i got them that i had one hen that seemed to be very old. too old to lay. she was quite a big heavier than the others. comb was almost a maroon color. she coughed and had what seemed to be a little rattle in her cough. i treated them with teramyacin which read on here does not do anything for that. did not help but they still look fine. she died about a month ago. now i have another older hen doing a sneeze cough type of thing but no rattle. i thought it was just from them being very old but after reading on here im a little nervous?? any advice appreciated!