What Causes Brown Spots On The Vagina?

If someone has brown spots on the vagina what would it be? It started out with one near, but then another slowly appeared, then another. Now there 5. Shaped like a little island on a map. I m not sure how else to explain it. No discomfort. Nothing different in diet or exercise. First one came about 5 months ago. The rest was recently. Not sure when but at least a month or so. I am concern because there more and coming faster. Thank you for your time, I look forward to hearing from you.