Hmm... it could be pigment that is affected by either age or sunlight and is starting to progressively change color over time. In which case, there isnt much you can do except wear subblock to try to prevent further discoloration. There are some new laser treatments around that are used to lighten dark pigmented skin such as birth marks and freckles. You might want to look into that. It is also possible that your hormones are changing and that you are starting to develop hair follicles under the skin. They may just not be coming out of the skin yet. If that is the case, then you might see if you are a candidate for laser hair removal which targets the dark pigment and destroys the hair follicle even if it is not above the skin.