I want each object to track its own health

I'm spawning multiple instances of the same enemy on screen at one. when the player "destroys" one, its destroying all instances regardless of when I put on extra conditionals to make it specific to that one. Right now I'm just making it so the one that is withing a certain range ( >100px away) is attackable, however one attack still destroys all instances

You need to add the Pick event to set which one you want to destroy.

Try posting a capx, so it makes it easier for us to help you out.

Not being able to see your code, I am almost 100% certain that there are something wrong with your picking, when you destroy enemies. Either double check it, or post a screenshot and I think a lot of people in here can tell you where it goes wrong.

I had the same problem but I fixed it with UID and Pick event.

Try the Selection by UID and check the range, it should work

Are you using the system condition "Compare two values"? Because that won't pick objects. You want to use the object's "Compare instance variable"