Have 15 chicks that I got when they were 3 days old. Different breeds. They are now 6 weeks old. All doing well in their breeder this morning. Nothing unusual. This evening I found 8 dead chicks and others that act like they on on their way. Whats going on? Nothing has changed. Water and food the same. Keep brooder extremely clean. Have booder in the house with temp at 85 to 90 degrees. They are droping like flies. Looks like they will all be lost. The ones left are breathing very hard.