Those events need changing a bit. Get rid of the on created events. On the top event where you spawn the object here you should set the enemy variable to spawnzone.UID and also add 1 to the spawn zone variable. Also you need to get used to pick conditions with objects not System. Use the object and use compare variable.
To explain the problem in more detail - when you use enemy on created : set variable to spawnpoint.UID again you haven't picked a spawnpoint. It doesn't assume the one it spawned from when it is a new event. You should try and do as much as possible in the event where the instances were picked.