You have to find out why the AI Perception component is detecting the enemies. Investigate a little bit about that. I can’t do all the work for you ;).
PS: They are all chasing the player, that’s not the problem. The problem is that they are also chasing each other.
Edit:
Here’s the solution for that problem. Haven’t tested it myself.
UE4 - Team Sight AI Perception Enemy Detection Affiliation C++ - YouTube