What's the max PSI rating on the tire? Did you check them hot or cold?
A lot of tires blow because of rubber valve stems. If you checked the air pressure before leaving, then drove 30 minutes a valve stem could have given out. As the tire looses pressure from the faulty valve stem (from road vibration), it can quickly disintegrate the tire. If one was rotten, it only makes sense that the other one would be too. Very common.....
