I have 5 chickens that have been battling a respiratory infection for about 3 weeks. They are about 15 weeks old. We've done a round of TerraVet in their water and they're still sick. They have coughs and clear nasal drainage. They are still active, eating, and drinking. We went to the vet today and they didn't really know what to do. They said the chickens overall appear healthy. The vet recommended a round of Tylon. Has anyone else experienced this?