Not noticing that you had 03.5 and 03 rims, especially from front and rear same side seems pretty unliekly. Those rims are alot different and even a blind person would have noticed.
Did u use a cleaner that your friend suggested you use, u know to remove the dust, and now you have stained them darker.
Good luck with Mazda, especially after 6500 miles.
My suggestion is to place both dark rims on one side of your car then go to Mazda and claim that the sun shines on that side of your car, and has damaged the rims. They will scratch their heads and more then likely change them for you under warranty.