These work fine. There's already a way to have a stuff done flag attached to a characer, so, when you kil it, it doesn't reappear. The chain of specials may not be reaching them somehow. Rearrange the order the nodes are called or have those creatures appear by a special node triggered somewhere else. I believe it should destroy everything within that rectangle.
Any help is appreciated.
There's no way to do this, although, these days, I recommend that people move away from the white spot thing. I'm afraid, at this point, hardcoding the spot disappearing is the only option.