Yep I had too.
I posted a thread recently about it, I also thought it may be overfeeding but whatever I did Noah would continue to have stools coated heavily in mucus, sometimes they were loose but don't recall any bad diarrhea such as you describe.
The minute I switched him off it the mucus cleared up so I figured something in Ziwipeak was causing bowel irritation, so I stopped.
He still has bits of ziwipeak as treats at the moment since I have a few pieces left from a trial bag but I don't feed it as a meal anymore, it's a shame as so many people here seem to rave about it and Noah also loved it and the little stools were great lol.
Still trying to find a food that 100% suits him
How many pieces do you currently feed?