Two weeks ago my smallest hen (the one that was always the runt) started sneezing and coughing. Within an hour she was dead. I out the rest of the flock on two weeks of Duramycin-10. they came off that last night. Tonight one of my barred rocks is looking like she doesn't feel well (ruffled feathers, appears to be sleeping but not sure). What's going on in my flock? I've never encountered this. It seems to be picking one of my girls off at a time. We live next to a river that's on the flyway and we have lots of Canada Geese, gulls, and herons right now. They have no access to my girls but I'm very worried. Coop is clean and they have good food and lots of fresh water. Can anyone give me some ideas of what this could be? Thanks.