I lost a pullet a few days ago. She was a bit depressed (inactive and slightly puffed up) one day and dead the next. A few hours before she died her rose-comb and wattles turned purple and I could hear a slight gurgling as she breathed (I had her inside under a light, giving her electrolytes and yogurt - as much as she would take, which wasn't a lot). The only sign that anything was wrong prior to that was a dramatic drop in the flocks egg production a day or two before. Unfortunately, we'd just had a cold snap and I attributed the reduction in egg production to that. I spent most of the day in and around the barn watching my remaining 48 hens and saw that two others were looking depressed. By the next day there were four sick, one near death. At that point, in fear for my entire flock and not knowing what else to do, I treated them with the maximum dose of water soluble tetracycline hydrochloride and saw immediate improvement. Today, none appear sick. I will treat for a full 7 days and hope that does the trick. The thing is, my girls symptoms are not consistent with Coryza or MG. Are there other respiratory ailments common to chickens? Do chickens get "colds"? Should I assume that it is Coryza or MG and that my entire flock will be contagious carriers forever? I could really use some help here. Thanks.