How many layouts do you have?
I think maybe you are running all the event sheets at once.
I suggest creating a layout for each level event sheet. On the selected layout, go to its properties on the left side, set to your desired event sheet.
More layouts won't really increase the memory size, because you already have the object image in the game.
If you create all events onto one event sheet, it will definitely slow the game down.
Hope that helps,