sumi
Rest in Peace 1980-2020
It may not be as bad, hopefully! I've had respiratory issues in my flocks over the years, with the odd bird. It didn't spread, but then it depends on what exactly the issue is… Hopefully yours got nipped in the bud now
Ugh I hope you don't have to do that. I would go look over at backyard chickens if I was you, maybe ask some people there. It would be too bad to cull them if there's something you can treat them with, and there are some pretty serious chicken folks over there. I don't hang out there, don't care for the atmosphere, shall we say... But if I have a poultry question, that's where I go. Hope you figure out an answer!
You may want to find a vet? If you sacrifice a chicken and have them diagnose you may get an answer as to whether it's treatable or not. No sense in wasting medication needlessly - or culling an entire flock needlessly. My husband (who is a veterinarian) says first thing he would look at for respiratory issues in a chicken flock is environmental, like high ammonia. He also says my advice above is reasonable.