My 8 year boy recently got four Isa Brown hens and they have been laying for a few weeks now. I have been away for a couple of weeks and for just over a week now he has only been getting 3 eggs instead of 4. He got a few double yokers just before they dropped to 3 eggs per day - not sure if it is related. Now one hen is looking poorly - comb is small compared to the others, hen looks swollen at the front. It is eating OK. Any ideas where to start?