I have 2 hens, we've had them since they were 5 weeks old. They're now just over 6 months. One of them (Hurley) has always been stand offish and a loner. The other one (Kate) was always very friendly, loves being held, good with kids. As of this week suddenly she's gotten mean, I was out visiting them and she bit me hard enough to leave a mark. Is this normal adult hen behavior? Neither have laid eggs yet and they're both buff orpington.