Sphinx, that's awful. And haven't you had some birds exposed to the "sick" hens longer than others, without them being ill? Is there something in the coop or where they run around in the yard that they could be getting into? Although, I would say that if this is happening at two week intervals, it could still be some kind of sickness. I think you've already posted something about this to the sickness and injuries section, haven't you?