Very dark, not black stool

Hi all,

I am beginning to get mildly concerned here. For the past couple of weeks I have had very dark stools, tho not black. They are not evenly colored either, parts may be darker than others. This is a new change for me. The stools are not loose or tarry, they are well formed and normal in consistency. I also have no pain or other symptoms. I recently began drinking coffee, but I stopped and there has been no change.

Like I said, I am otherwise asymtomatic, tho I have noticed perhaps a small tendency that there are small amounts of undigested food in the stools, tho that is not always the case. Again, no visible blood, not tarry and not black. Just dark brown. Negative other symptoms. Should I be concerned? It's been about two weeks. No change in diet or routine either. Thanks!