Sorry about your NN, it sucks when they die...let alone mysteriously. I have a hen that had a very minor prolapse..it went back in itself within 24 hours. I'm pretty sure it was her first egg as well..she was born Jan 1, so 5.5 months or so. Pretty sure it was her first egg -- and it was itty bitty at that. No clue what happened there. I have only had one other minor prolapse and that one recovered. not sure if the other hens had pecked at it - NN might be more prone to that sort of thing with a bare rear. Going to try and hatch more replacement NN's soon with luck.
Just went out to open up a new bag of flock raiser and it had little white mites crawling all over the bag
