Sounds kinda like Ellie. She does fine with Metro though. In one of her bad IBD times, she had some blood in her stool and she got through it just fine.
They can get it when their intestines are angry. Found the right food for her pancreas and intestines and she has been doing ok.
Stress can definitely set some intestinal issues off. Whether it is that or he ate/licked something that bothered him, or it came out of nowhere you'll probably never know.