I received a new flock of chickens approx a month ago, within a couple days I noticed the one sneezing and coughing. I'm new to chickens and didn't really think of it as a big deal. A week later I noticed her eyes were slightLy watery. I decided to separate and put her in a large crate in the garage. I gave her extra garlic, acv, oregano oil and other herbs for about a week. Her symptoms didn't change, I then decided to put hr on antibiotics starting 6 days ago... I have been giving her an 1/8 of a teaspoon of duramycin in 2 cups of water and changing it every days her symptoms are still there. She may be a touch better, but she'd still coughing, and making a purring noise when she breathed sometimes. Now one of my other chickens that have been outside separated from her is starting to cough. Why is my chicken not improving and why is my other chicken showing signs of illness. What can I do? All of the chcikens are feed non gmo layer mash. I use straw for their bedding, which is cleaned out regularly. Are given acv once a week, garlic in their feed and oregano oil. It's frustrating that I do everything in my Power to provide them a clean home and feed high quality food with supplementation. Thanks for your help and advice in advance.