Give the enemies an identification code (on creation) by use of an instance-variable. Then add an event that checks that instance-variable.
By instance. Give the enemies an instance-variable 'id', make it 'text'. Give 'id' a value when you create enemy. First enemy, value = "Peter". Second enemy, value = "John" and so on ....
Then add a condition thogheter with the Y-checking: instance-variable of enemy = "Peter" > do this
Dont have to be text, ofcourse, it is just easy to explain that way.