I have owned 5 Mazdas.
My 2003 Mazda 6 began rusting around the rear tirewells.
I had it recently repaired.
My son's 2004 Mazda 3 has the same problem.
It is rusting and the paint is starting to bubble.
Anyone have this problem?
Should I contact Mazda?

 

Why would you contact Mazda? The cars are 7 & 8 yrs old now.
Chances are its road salt that's caused the problem. I used to live in Pa and we had that problem all the time up there.
The only thing you can do at this stage is have the cars repaired ($$$) and power wash them down reguarly, especially after driving around on snow and ice.