2008 FLEETWOOD UTAH Tires Problems

I PURCHASED A SET OF FIVE (INCLUDING THE SPARE) NEW CARLISLE TRAILER TIRES IN EARLY 2009 FROM DISCOUNT TIRE IN COLUMBUS, OHIO. THE TIRES ARE CARLISLE ST205/75R-15/D1 RADIAL TRAIL. THESE WERE REPLACEMENT TIRES FOR THE ORIGINAL TRAVEL TRAILER TIRES WHICH WERE A LOAD RANGE C, THE RADIAL TRAIL'S ARE LOAD RANGE D. SINCE THAT TIME ONE TIRE FAILED DURING A TRIP IN JUNE OF 2010 AND WAS REPLACED AT A DISCOUNT TIRE IN OGDEN, UTAH. LATER IN OCTOBER OF 2010 ON OUR MOST RECENT TRIP THREE OF THE REMAINING CARLISLE TIRES FAILED. I REPLACED FOUR TIRES AT THAT TIME IN OKLAHOMA CITY AT A DISCOUNT TIRE. I HAVE SINCE PLACED MY TRAILER IN STORAGE. UPON INSPECTION OF THE TIRES ON MY TRAILER I NOTICED SIDEWALL BULGE ON TWO OF THE NEW REPLACEMENT CARLISLE TIRES EXACTLY IN THE SAME SPOT AS THE FOUR TIRES THAT FAILED. THIS IS WITH LESS THAN...