I did more searching and found this posting on Tesla's forums:
Orange residue below fog lights
The links for the pictures he posted are messed up in the forum view, but they are here:
Orange marks
Orange marks
IMG_3383
This is based on the rusting metal bumper reinforcement that mongo and MP3Mike mentioned previously on this thread. The pics that MP3Mike posted were far more extreme than what I am experiencing, however the pics that nickjhowe posted over on the Tesla forums (the flickr pics) look a lot more like what I posted. So I am wondering if Tesla never did actually fix/modify these metal bumper reinforcements after all these years.