Self switches are local to the event. Turning on a self switch on one event does not affect what happens on other events.
If your troop consists of 4 slimes and you have events for them all, use a switch rather than a self switch to turn them off.
Also, you don't need the first page of your slime events. Having a page with no sprite and no conditions, then a second page with a sprite and conditions, is exactly the same as having just the second page with the sprite and no conditions. You don't have to have a first page to say "don't show anything if the conditions on the other pages aren't met".