Right after Easter, I bought 4 2 day old baby chicks from my feed store. All were doing very well. (2 Buff Orpingtons, 1 EE, and 1 unknown). 3 days later I bought a 3 day old Crested Cream Legbar. Then I read that a local breeder had Blue Copper Marans, so I put hazed 4 of them for $15.00 a piece. Same day I went to the first breeder and bought 3 Blue Laced Red Wyadottes. When I got home I noticed that one of the blue marans were very weak and could hardly walk with a second one out of the four not as active as the other two. I really wish I had isolated the breeder chicks before adding them to my brooder. The next day. ..the weakest blue maran died. Next day, second blue copper maran died. I called the breeder and he offered to replace the two that died. Then I started hearing one of my BO coughing and acting lethargic. Went to the feed store and they recommended Vet Rx. I thoroughly cleaned out the brooder with a vinegar solution and all their feed dishes. Yesterday one of my Wyandotte died....and this morning a third Blue Copper Maran died. I don't know what is going on. I've NEVER lost chicks before, however, all previous chicks were from feed stores or I hatched myself. I don't want to loose any more chicks. Anyone have any recommendations? HELP!