We've lost 2 hens the past two days and another sick today. Not a mark on them, appear healthy one day, the next day they're ill and by night they're dead. Comb gets pale, breathing appears labored, don't appear to be egg bound. Bodies are not puffy, don't seem to have a full crop. No chemicals or other substances in the yard. Food has not been altered... water is clean. These are all banties, different breeds and have been a happy little flock for about a year. The two full size hens seem to be immune, at least for now. Any ideas would be most appreciated. Our flock of six is down to 3 healthy and 1 ill. At this rate by the end of the week we'll be down to 0.