It's unfortunately "common" that RV manufacturers put on HORRIBLE tires from the factory. When a big 80-85 series tire blows, it can cause pretty substantial damage.
Part of it seems to be due to tires that are running close to capacity limits already and then they age (probably dropping max capacity by 10% a year).
Tell us the following:
Size and model of the tires
Give us the DOT code on the side
We'll be able to provide further advice.
I have a 2015 Keystone 5th wheel. It weighs about 13k unloaded on two axles. I replaced the factory tires after driving off the lot... Provide tire info before you go do it though, it may be unnecessary.