I have been seeing two of my pullets, who are about 5 or 6 months old, starting to fight all the time. One is my Barred Rock Pippin and the other is a White Leghorn cross Merry. The last day or two, if Merry is near Pippin, Pippin will go after her, bumping her breast and fluffing up her neck feathers. Sometimes Merry will do the same and they will fly at one another...they use to be good friends...why does this happen or is it something else?