Ok. You need a way to store the tile that is going to be occupied by each unit that moves and check that against the other units when finding a path. I'm not familiar with EasyStar so I don't know if this is supposed to be built in or not.
Normally I would flag the position to be moved to with a variable, or a change in tile state, then exclude that from being a valid path for find path events that follow.
You would do this using loops. I will make a small example when I have more time to show the logic of it.