I didn't get any stones or any evidence of anything green on the fourth flush I just did either.
It could be because I didn't wait long enough between Liver Flushes or because I was taking chanca piedra for a couple of weeks before my third cleanse (which seemed to break up the stones a lot), or, I wonder, if I just don't have stones left?
I think that would be doubtful though as the stones I saw on my first flush didn't look old.
I'm going to keep going at it though, it must be doing something.