Is It Normal That I'm Having Dark Brown Blood/discharge? I

Is it normal that I'm having dark brown blood/discharge?

I am nine months postpartum I had what I thought was my first period last month very light dark brown for five days and I didn't think much of it because I didn't bleed long after birth and suspected it was just old blood, but here I am again with it on day six of this month and I am concerned again for the color.

Before pregnancy I had heavy periods that would last for extremely long times, so this spotting/light brown and for such a short time is very different and scary for me. The very first day there was some light pink, but I've had nothing but dark brown spotting sense. Should I be concerned? I am 20.