I had a male with four females, all hatched together. One day he just flipped his lid and started attacking everything, hens included. Then he tried to attack me when I found two of my hens bloody, so the butcher attacked him.
It is amazing how fast they seems to turn. Overall, I really enjoy raising coturnix so far. They are gregarious little birds with interesting behaviors.
I've found the white birds are usually the ones to get picked on first. Those white feathers, spots of brown, so easy to pick, then pink skin or blood spots just make it worse. If I have a white hen I want to keep for breeding I keep it with other white hens, less "racial" tension that way. White roos go in the freezer.