My 'simple but might work' thought is have two global transitions. One when a key is up (player isn't putting input to move) and another when input is received. Without input/movement have the drones stop. When the player inputs to move (button/key/joystick), fire a global transition to move the drones again. The second drone just follows the first drone instead of the player. Just get position of whatever it is following every frame, or do a 'get position', move to position (itween), on finish, check input/no input. If no input, go to a state that waits for the global transition. If still input, get position.
So the drones will stop the moment the player stops and move the moment the player moves. If they move the same speed as the player, they won't 'catch' the player theoretically?
No array required.
Edit: You could also make an empty game object as a child of the player, or a cube with a collider and no mesh renderer, and use it's transform as a target to keep the drones farther away.