Can u clarify on "together" . Do you mean they in the same tank or do u mean they paired up. If they only in the same tank but not paired up. When u introduce a hosting coral will increase the teritorial reaction. As for the other damsel simply just pick on the " weaker" one simply it is their nature behavior. If the clown were paired up, it could just a sight for fighting for the " dominant" one out of the 2, and the one winning will become the female is the two. I would suggest remove the one losing the fight if it is not a mated pair. I would remove the damsel if they are a mated pair