Black cherry soda and dark stools

Can black cherry soda cause dark stools? I've been drinking black cherry soda for the past few days and have noticed that my stools have been dark, but not tarry. I haven't taken any OTC items containing bismuth. I usually take Prilosec for my GERD. I also have IBS, anxiety and depression as well. And I am undergoing a lot of stress right now too.

I did, however, have some diarrhea recently with bloating/abdominal pain. The dark stool started showing up after the diarrhea.

I've had my stools tested in the past and also has my upper GI and colon checked, but everything had come back normal other than having polyps in my colon which came back non-cancerous.

I just don't know with the GERD and IBS if it might be blood or just the dark color of the soda causing it...

Any ideas?