Google "Infectious Coryza." Your free rooster could have been a carrier and bought it into your flock. If so, all your birds who have been exposed could get sick and all will be carriers for life. There is a test call a Poultry Respiratory Panel that can tell you if that is what you are dealing with. It's expensive, about $150 plus shipping of the specimen. We just went through this after bringing in a $5.00 OEG bantam rooster I got at a small animal exchange and being dumb enough not to quarantine. But after tons of research and money I now realize that even quarantine doesn't guarantee anything. The bird could still be a carrier and not be sick himself. Luckily the tests were negative, he just had a bacterial respiratory infection which he passed on to the first hen he got into a fight with. We almost lost both of them but without knowing we might have had to cull our entire flock.
I am sorry you are going through this. It was horrible.
Good luck.
Mary
p.s. I have now closed my flock to new chicks, pullets, and adult birds. If I don't hatch it here, it isn't getting in! There is still some risk with hatching eggs but I will buy only from reputable sellers.
