I Am An 83 Year Old Female. My Bowel Movements

I am an 83 year old female. My bowel movements have been dark green (formed, not loose) for the past 2 weeks, accompanied by lower abdominal pain and a consistent bitter taste in my mouth. I have chronic diverticulitis and IBS episodically, but never have experienced this change in stool color. I haven't consumed spinach or leafy vegetables, nor do I take an iron supplement. Should I see my gastroenterologist about this?