Are you talking only about some discoloration, or the location and shape of it as well. I've not seen that particular color or pattern myself.
If the coach has a clear vinyl film (aka paint protection film) on the front, mold sometimes forms between the film and the body after several years. The fix is to remove the clear film. The film gets dinged with stones and moisture gets in, allowing mold to grow. However, I don't see evidence of the film installed in that photo, but it isn't very visible to begin with.