one of my cornish cross sounds like it is doing hiccups too. Iy could also be sneezing. I have 5 and it is really hot and humid today and they are all panting loudly. They are about 7 weeks old. I have put some electrolytes in their water. I will go and check on them again in about an hour. They also have very watery poo. I am thinking they are probably too hot, especially as they are getting so big. I don't think I will be doing cornish cross again they aren't natural. The 3 other chicks asian blues that are the same age are not having any problems and are behaving normally.