Question Which team is actively learning?

I am making a 2-4 player board game. So there are 4 agents, each with a 0-3 team number. I am training for all possible number of players, so some games will only involve 2 agents, while the other 2 sit out. How do I know which agent is the "active" one that is learning (whereas the others are ghosts/past snapshots)? Because I don't want for one of the agents not playing to be the one that's supposed to be learning, while the 2 actually playing are ghosts. Thanks!

 

Bump.

I am setting the agents' game objects who are sitting out to inactive. Will ML Agents automatically detect this and only train the ones who are active? I am considering "scrambling" the agents used by each character at the beginning of each game, which could mitigate any of these potential problems, but don't know if this is necessary.