anyone else having this discoloration?

Attaboy

i wash the car at home by hand. i only use soap if she's really dirty. this car will NEVER go to a carwash unless i can find one who will wash by hand and who is as OCD about their car as i am.

most of the time i just use a damp synthetic chamois to wipe off the dust. if i do have to use soap, i use as little as possible, and only where needed (usually front bumer and for getting soot off the exhaust tips). i assume we all know how questionable the paint quality is on our Z's and what soap can do to a car's finish when you're trying to keep it showroom sparkly.

i had originally thought washing may have something to do with it, but when washing, the water does not get into the area where the discoloraiton occurs.