I got DAY GLO ORANGE sludge in copious quantities on day 57!!! It had been stapled (velcroed?) to my poor abused colon for heaven only knows how long!
You can get gunk out at any time while cleansing. Do not add psyllium while fasting or risk terrible gut aches/clogging. Wait until you break your fast to add psyllium and your pro-biotics.
My excellent naturopath has me take 1 tsp. psyllium powder with lots of extra water 3x daily when breaking a long fast until digestion is fully reestablished. The break is the time to add the probiotics etc.
Consider a professional colonic (or better, a series) to make sure you've gotten all the gunk your fast has loosened. Now is a great time.