My 3+ year old Buff hen is coughing and mouth discharging clear/green and her comb is pale. When I pick her up the discharge almost constantly flows out and it looks like she going to pass out. She had this in a milder form about three weeks ago but the discharge was clear. I treated her with terramycin for three days and she looked fine. Gale's Chicken Health Handbook doesn't mention this green mouth discharge. What can this be? Or is it time to put her down because of chronic illness?