I'll try to get pictures up. The brown marks almost look like rust-colored (or tan colored) corrosion but they are on plastic so I guess something splattered. There is not a lot of this but I am worried this is the beginning of something bad. It is also near the passenger side headlamp area of the black metal 'deck' in that area. (The place where one might rest a wrench when working under the hood). It is as if something came down from above. I can't seem to trace a source. Maybe oil is being kicked up by a belt? It is not a big mess. Any ideas?