firestone tires

Well here we go again had st235/80r/16 on my trailer 2007 Montana. So far this trip have had 3 blowouts. Need I say not happy. Tires are less than 2 yr old and only about 3000 miles. Did a lot of damage to the trailer but it was all cosmetic thank god. All the tires had 80 psi so under inflating was not the problem. They are firestone tires or shouuld I say were.