Wednesday morning I noticed most of my 3 month old chicks (about 15) we're acting lethargic. The day before they were acting normal. 8 hours later 4 were dead. 4 hours later 4 more died. I gave them fresh water with a dose of Corid they drank and went to roost. This morning 6 more we're dead. I freshened their water water and 8 hours later 10 more we're dead. I've gave them a second dose of Corid an hour ago. I'm down to 11 chicks. They are a little more active than yesterday but still sick. They are in a coop by themselves but my older hens and Roos free range and get pretty close to the sick birds. Should I be giving them Corid also. And how do I sanitize the coop if they make it or not.