Hi, spicey! Not sure if I've said welcome yet, but welcome!
Two thoughts on the peppermint capsules. First, if you don't want to spend the money, you might try Altoids or similar peppermint candy or peppermint tea first. I learned the hard way that I have GERD (heartburn and gastric reflux) and that peppermint is a no-no for me. I have two jars of peppermint capsules sitting in my cupboard that I bought and can't take!
Also, if I understand your question right, you're talking about using peppermint to stop the diarrhea. It won't do that. That's not what it's for, it's for the crampy pain. It won't help with the D at all. At least that's my understanding and my experience.