SWF not as effectve as it was in the beginning?

I am on day 20 of a 21 day fast and the swf was working like a charm until day 18. On day 18, 19, and 20(today), the swf just doesn't seem to be working like it did. It is taking longer to "happen" and I don't feel like all of the salt water is coming out. I haven't changed any of the measurements. Has anyone else experienced this? Other than that, I feel great and this cleanse has been a great experience, I am looking forward to my oj on Monday! Good luck to all.