I made a rookie mistake and introduced new chickens into my flock without keeping them separate first to monitor for illnesses. Banging my head against the wall now trying to figure out who to treat for what. I have 4 that sound like they have bronchitis. 2 are from my existing flock, and 2 are new. The new ones, along with a few who are not coughing have very loose, if not watery stool. I have everyone who I know is sick separated. I put 1TB of oxytetracycline in a 1 gallon water bowl. I didn't see them drinking much so I very slowly syringe fed some to them. Is there anything else I should be doing. The girl at TSC told me to get that but I'm wondering if I should have gone with the Tylan injectable that I have seen on posts here. Should I switch? Is the diarrhea related?