If they have not been there long they are getting used to the tank. Once they do they will be establish territory, in a small tank that happens really quick. After that they will establish hiarchy, and I betting the 3-stripe is going to win. If they continue for more than a few weeks and nothing is wrong with you water (
ammonia, nitrties) than they most likely will not take to the tank and they are going to stress out. If this happens than you could removed them and try with other damsels. Fish are llike poeple they all individuals and no two fish are the same.
Also damsels are not really swimmers like the tangs and wrasses, but they do chase each other around untill there is food in the tank.