Julie, I had the same thing happen on my 9th day of this MC. Lots of dark mucus and some solids, plus really smelly. I figure its either toxins flushing out from all over the body, or the impacted fecal material in the colon breaking down. Whatever it is, I'd rather have it out than in. One reason I think some of it may be from some source other than the colon is because on two of my Liver Flushes
I had similar smelling fluid pass with the stones. I named this stuff "putrid bile" because I assume it was bile whose flow had been blocked by the large stones, but this is just a guess. I did go ahead and start weaning off Master-Cleanse
today (my 12th) because I want to do a Liver Flush
tonight. I have been having vague pains in the liver/gallbladder area and I think I need to do this. Also, my tongue is starting to turn, its not quite pink, but its not the gross pus green color anymore. And most of all, I am getting hungry, not just wanting to eat, but needing to eat. Anyway, I don't feel 100% detoxed, but am much cleaner than when I started. I will be doing some high fiber bowel cleansing in the meantime to keep the cleansing going.
All I can suggest is that you listen closly to your body,if you feel you need to come off Master-Cleanse
and go another way, then do so. You have been a real example and inspiration to me, congratulations on your success.