I was just talking to my doctor over the phone about this this morning. If it is bright red or light red, it could mean hemorrhoids, a fissure, or just plain irritation from having too much diarrhea. But if the blood is ever dark or you have dark stools then the blood is coming from somewhere in the intestines and/or colon and needs to be checked out asap. You are very lucky that the Metamucil helps with your diarrhea and that you can even eat any of those things. I got my gallbladder removed 7 months ago, and I can hardly eat much, diarrhea and nausea are almost an everyday occurrence, I completely lost appetite and I've lost 40 lbs. My doctors are STILL trying to find a medication that will work for me. Good luck.
Bright red blood on toilet paper is usually hemorrhoids. If it continues, I would get it checked out just for piece of mind.