I have two broody hens that are together raising a batch of 14 chicks. They each hatched half the eggs in ajoining nest boxes. Overall, I would say they are splendid mothers. They are in general very caring very defensive of the chicks. They both are raising the chicks together as one group However, there is one chick that they both seem to hate. Periodically they will get very angry and start attacking it. I just cannot figure out why they would do such a thing. Once one hen goes after it the other joins in. It is just terrible! They are really brutal and I believe they intend to kill the chick. Is this common?