I am a new backyard chicken keeper. I have 6 hens now 9 months old. I have 6 different varieties. Recently I have noticed that 2 of my hens are pecking on my Americauna. The bully's I've seen have been my Astralorpe and my New Hampshire Red. They have pecked her feathers off behind her head. I'm afraid if this continues they will kill her. Need suggestions, please!!