Wheel picks and paint chips

My wife and I have owned a 07 XR, AWD with 19 inch wheels for a year in September with 25,000 KM on it. We live in Canada and have snow covered roads for roughly 4 months. In February I noticed the clear coat on the back wheels start to pick and the aluminum was corroded, the black plastic below the doors is picked and discolored, and the paint is chipped behind the rear doors. I think the front wheels are throwing sand (used for traction on icy roads) towards the rear of the vehicle. My wife and I take great care of the Outlook, and had the dealer install mud guards when we purchased it, and only travel on paved roads. After many discussions with the dealer, they have turned their backs to us stating that it is road debris and is not covered under warranty. I have owned many vehicles and have never had a problem like this, and after checking around I do not see anyone else driving a Lambda having similar problems. It is very frustrating looking at a new vehicle and seeing this. We are also fed up with Saturn, I feel it is a design flaw since the tires are to wide and they stick out beyond the fender. Other than this problem we love the Outlook, but are considering selling. Does anyone have similar problems, and did you have any success with Saturn on a fix. Has anyone seen an aftermarket mud guard that is wider than the Saturn brand.