Hello Doctor, I Am Now 9 Days Post-op Appendectomy And

Hello doctor, I am now 9 days post-op appendectomy and believe the procedure went well. For the first few days I didn't have much appetite but attempted mainly soft foods and soups. For the last 3 days I have slowly introduced solids into my diet. But for the last 2 bowel movement, usually once a day, has been unusually dark, should I be concerened? I have a follow up appointment tomorrow at the hospital.