one of my 22 day old cornish X has been going downhill for several days,I noticed it seemed to be breathing a bit harder then the rest then it started getting weaker,its eyes are clear,nothing around its beak,stool looks normal,it stands with its head down,feathers ruffled,with its eyes closed,no pasty butt,I haven,t been doing anything different,same feed,same water,bedding clean and dry,I can,t find signs of anything,it still eats a bit and drinks,,,I don,t know what else to look for or what to do,,any advise would be appreciated,,mxpres