Not to be ominous, but I had a pair of golden dojos before my current pair, and they both did roughly what you describe, separately, the day before each died.
I got another pair from the same LFS, from the same stock I believe. They've done fine. The only thing I could think of as the possible cause was temperature shock. It seems like many LFS insist on keeping Dojos with tropical fish, and I may not have allowed enough transition time for my cold tank.
For your case, the suggestion of constipation certainly seems possible. I was shocked a couple of days ago to witness one of my 4-5" golden dojos produce a bowel movement the like of which I had assumed was coming from my 10" common goldfish. I was blaming the wrong fish for making such a mess of my tank, and I'm not sure if a diet change might be in order.