I purchased 8 Cornish cross, 3 ducklings, 4 black australorps and 4 Rhode island reds. the Cornish are about 2 weeks older than the rest. i lost 2 reds the first night(4-1-17) then yesterday i lost another red. the Cornish are doing great, the blacks seem fine and the ducklings are all OK. the other red seems OK. are the reds more prone to stress or disease than the others? are they less tolerant of temp changes?