Here's the story, I got 6 hens who I thought simply needed to be treated for lice and scaly leg mites. I treated them with ivermectin pour on drops 2 times every 2 weeks. One was an americana who barley ever laid an egg, she popped one out when I brought her here, within 2 weeks I randomly found her dead. She only laid 1 egg within those 2 weeks. 3 weeks later, another hen had to be euthanized, she was dying and would not stop having diahhrea. In this 3 weeks, my rooster who was over 5 months old got into their coop and ruined my quarinteen process. So I said whatever and let these birds out from their shed and let them roam with my birds. Over 2 weeks ago, the crippled hen (she has only one good leg) got her eye poked out by I'm guessing the rooster? After this happen, I could could see she was breathing more deeply, her wattles would go in and out like heavy breathing. The next day I could hear her breathing, I was about to euthanize her too because she barley reacted to me pushing her with my foot, but my mom wouldn't let me, this is her (pet) so the next day I treated her with a herbal remedy twice a day for about a week.Her symptoms were heavy breathing, darth vador breathing, and bubbles in her eyes. No mucus and was eating. She's good now, cleans herself, walks around as much as she can, and pecks at the ground. The thing is, if she has/had and upper respitary infection, why have none of the other birds shown symptoms of it? Since she got sick, I have noticed they sneeze, but that's it. It seems like normal sneezing sounds to me, nothing dramatic, nothing that happens often. So anyone have any what's up with the heavy breathing and bubbles in her eyes? She doesn't have bubbles in her eyes anymore, but her breathing does still look a little heavy to me, but I don't hear her breathing anymore for the most part. It's been almost 3 weeks since she got ill, I would except the other birds to be sick by now too. Also what baffles me is that I read that these infections are triggered by stress or can be once a chicken is exposed to a sick bird. But, why didn't they all get sick when I first moved them in? I don't have wild birds that can manage to fly into the shed. Unless my birds are carriers just don't show signs? No point in culling them all though since the possibilty of them getting it again is highly likley since they free range. So better to just use prevantive measures.