This is a simple picking problem.
You are not referencing the Enemysword1 in your first event, so all are selected..
You probably have a way to keep enemysword1 attached to each enemy, so you should be able to pick the right sword in the event..
So the event should be something like:
Enemy is overlapping
Pick attached enemy sword
set enemy sword invisible
spawn slash at enemy.x,enemy.y
enemyslash On animation finished
Pick right enemy / enemysword
set enemy sword visible