I Have A 15 Year Old Total Care Patient On

I have a 15 year old total care patient on Peptamen via J-tube. She is dependent upon daily liquid glycerin suppositories to produce a bowel movement. For the past few days I’ve noticed her stools have dark-colored, sand-like particles in it that adhere to her skin when I wipe her with baby wipes. I am flummoxed as to what this could be. They are grainy like sand and hold their form.