Small rust spots on the top of shell

I just noticed while I was cleaning the exterior several small what I am calling little rust spots on the top of the shell only in one general location about 4' in diameter at the rear. The TM isnt parked under anything and I didnt notice anything like that when I brought it home two weeks ago. They are like small, maybe the diameter of a pencil lead around rough protrusions. Like little rust spots starting. Weird because it is only on one portion of the shell. Nothing on the sides. Anyone ever had anything like that?