What Could Brown Specks In The Vagina Be?

Every now and then when I wipe my vagina I see lots of brown specks on the toliet paper and it looks like it is coming from the inside of mycoul vagina. There are no sympthoms nor ichting. I have taken a really good look at the toliet paper and try to figure out what it is, it just looks like a bunch of tiny light to medium brown specks. I have even touched it & it is extremely soft and dissolves when I rub it between two fingers. This happens every now and then, but it has been going on for years. I go thru this every two or three months, I just had my routine check up with the Ongyn, everything was fine, no STD's nor infections. I think it might be my skin rubbing off because my skin color is tan, this is something that is always on my mind, please give me any input. Thanks!!