I have four hens, some one year old and the others eight months. They have always been separated into two groups of young and old, and they have been dear friends in each pair. But then I noticed one of the younger hens furiously attacking her friend. It started this evening and just a few hours earlier they were friends but now my submissive hen runs away when her old friend comes near. What has changed her behavior like this suddenly? Also, the submissive hen has not laid eggs for at least three days, unusual for her. Is she stressed because her friend is not being nice to her anymore? Or some other problem? She doesn't feel like she's awaiting an egg either, and is comfortable when I hold her, and is quick on her feet. Could my aggressive hen be undergoing spontaneous sex change by chance?