So last year my chickens got sick. They started sneezing and around their eyes were swollen. you could also hear them having trouble breathing. I ended up losing a couple of birds and ended up getting them tested by the state. they came back clean and the sickness went away. I didnt add any new birds to my flock this year. Last week the same sickness came back. I lost numerous birds and am clueless as to what is going on. I tried apple cider vinegar and it doesnt seem to do anything. What is going on with my flock and what do i do?