How fast were you driving and was the trailer overloaded? Marathons are rated for 65mph. If you drive faster and are heavy they heat up. That said perhaps one of them may have been defective but two? I just replaced all four shoes with the Good Year Endurance. Load range E speed rated 80 mph. Just came back from a trip and they are designed to run cooler and they were as I checked them at fill ups and when I stopped.
Blowouts could be from multiple causes. Debris in the road, underinflation, driving to fast, to heavy or overloaded.
PS I had two sets of Marathons on my prior TT and never had an issue other than I wore them out. I liked the tire. I would have put than on this TT but they offered a upgraded version the Endurance, so thats what I did. The cost difference was negligible.
