Black patches on stool? (TMI)

I’m 8w pregnant and on prenatals with iron (so maybe that’s the cause)

I had a bowel movement today but it wasn’t anywhere near constipation it was soft stool/borderline diarrhea.

And when I looked it was floating, Brown with black patches. What could this be?

I’ve been taking my prenatals for a while and it hasn’t happened before. Could it be a bleed? But its not all black/tarry.

Any insight would be great!

It’s sunday so no doctors office is open here :/