I have a feeling that whether everyone knows it, or not, most of us have rust under where the radiator sits. I don't really have any rust on my VX anywhere, but when I was doing my timing belt swap I noticed rust right where you're talking about. I also noticed that the back side of my front skid plate (right under the radiator mount) was also rusty. Must be something about how the water drains and pools right in that area.