Potassium and magnesium are minerals, not vitamins, but that is just semantics. Hopefully you are supplementing based on your doctor’s recommendation. As you already know, potassium is critical for the electrical conduction of your heart, and overdoing it can stop your heart. If you have issues with internal scar tissue, you are better off avoiding high fiber foods and supplements. You should slow your gut with loperamide or lomotil, but only to the point that you absorb your nutrients better. After more than two decades, your innate function is probably as good as it is going to get. Magnesium supplements cause diarrhea, so another reason to slow the gut. But if you slow the gut enough, you should not need supplements for magnesium or potassium. The kidneys do a good job of keeping the levels normal (as long as your kidneys are healthy).
Jan