Two weeks ago Sunday our rooster started acting Lethargic then his comb started turning purple. He died 3 days later. We were heartbroken and thought it was a fluke. This past Sunday one of our hens started acting lethargic and has had a couple seizures. Any ideas on what is affecting our flock? We have had chickens for a little over a year. Last August we had a hen with contract a respiratory infection , treated it with Tylan 50. We had no other Issues till now.