I couldn't see the pictures, but was your little guy the same age as the others? I had a three week old Silkie in with a couple 2 day olds a year or so ago, and, not knowing hardly anything about chickens at the time, kept them all at the same temperature. It took me forever to realize the Silkie's labored breathing and lack of energy was caused by the heat. I'm sorry to hear about his death though, that's sad.