Weird end of the period

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Hey ladies! I’m very confused about my cycle and I need some answers. My period will look normal and healthy (red blood, medium flow, mild cramps) and then after about 4 days it’s no longer blood but it’s black and looks like powder. I don’t even know if I should log that on my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period tracker</a> as my cycle or why it’s black. It’s not even discharge, it’s like skid marks. I just don’t understand what it is or why it’s happening and if I could it as part of my cycle. Comment below please 👇🏼