How do I prevent overlap?

I've got all of these enemies, but they start to overlap each other pretty easily. Is there a fix that I'm missing or is this something I just have to live with?

You could give them the solid behavior, so that they won't collide with each other. If that doesn't fit/or is too clunky, you can create an event similar to this one:

With this event, it will pick the one on top and every tick it will move it one pixel to the right until it is not overlapping anymore. You can change this as needed.