This morning, we let our birds out to free-range for the first time in months because the temperature had risen a few degrees above freezing. I noticed that one of my 10-month-old pullets was coughing and wheezing. She had difficulty breathing and eating at the same time but her appetite didn't seem affected. This afternoon she was better, but was still coughing occasionally. My Cornish Rock pullet is also wheezing, sneezing, and having problems eating and breathing simultaneously. Neither of them had any nasal or eye discharge. All 5 seemed just a little bit slower and more tired than usual today. There was watery poo everywhere. I am afraid (but not sure) that they may be tired and sick but reluctant to appear inactive in front of me. They have all had occasional bouts of sneezing ever since they came down with a serious respiratory illness as chicks, but pulled through. I am sure they are carriers of something now, potentially multiple diseases, but I don't know what. Their coop this winter is NOT ventilated. It gets very humid in there. I tried to air it out today. I hate to isolate any of them, and honestly I don't know how I would. I have read up on respiratory diseases but they are all so similar that I can never pin down which one is affecting them. I will probably put some Nutri-Drench in their water tomorrow, but I am debating whether or not to treat with the Tylan 50 I have, or whether to use any VetRx (I know it's controversial). Does anyone know which disease this is and what I should do? Thank you!