Tire Sidewall problems of the 2008 Hyundai Sonata

The sidewalls have cracks in them, all 4 tires. They have been on the car for 2 years (installed November 2011) and have 6000 miles on them. The exact same tire that came on the car new, had to be replaced at 17,000 miles because of sidewall cracking. The original tires were 4 years old and all 4 had sidewall damage they have never been damaged and have always been properally inflated. The original tires were never damaged or under inflated. This is a manufacture defect and a safety issue. The car has never gone more than 7 days without being driven. It's usually driven every day or every other day.