Hmm loose mustard? do you mean sludge, diarrhea, formed stool that broke apart?
Were you passing clear water before passing the mustard sludge? If so, you know for sure it is biliary sludge.
The first 2 flushes could have removed your soft green gallbladder stones. This flush could have reached deeper and released more sludge from your liver. I had sludge release on flush 5 (along with stones). If sludge is your problem, try eating loads of raw garlic, cooked onions prior to your next flush.