I currently have 5 ducks. one duck is showing signs of I guess respiratory infection. it constantly gasp for breath/ labored breathing, coughing. We just got the ducks about 3 weeks ago, only one is showing signs of this. What can I give it? I'm going to separate it from the rest once I find somewhere to put it. If there are antibiotics where do I get them? The local tractor supply wasn't very helpful. They showed me this VetRx medicine but from what I'm reading it's mainly for prevention.