Anyone on Nexplanon have/had this problem?

Okay so I've had the Nexplanon implant for a few months, my first period was very light, more enjoyable than the ones I had before and I was very satisfied. The problem I'm facing right now is that I started my "period" like two weeks early. I put period in parentheses because it's not heavy enough, and I guess it's more of spotting? But the thing is the blood coming out is EXTREMELY dark, and very like powdery? Kind of TMI but when I get off the toliet it's like someone just dropped in crushed up red pepper. It's weird, I expected irregular bleeding but this is what irregular bleeding is? Sorry if this is confusing!