Issue: Very bad respiratory infection in 3.5 month old Welsummer chicks. Actions taken so far: Sunday: Injected .5ml of Tylan 50 to all birds (4). Monday: Hens recovered. The Rooster isn't. Inject 1.0ml of Tylan 50 to rooster. Tuesday: Hens looking good, still no improvement on rooster. Applied VetRx under wings and on comb on rooster. Wednesday: Early PM check showed no improvement. What the heck do I do know? Other information: Found some mites on birds (not a lot), I will seven dust them after infection is resolved.