Things that can cause that include overloaded trailer, under pressure tires, and bent axles. Whatever it is, it needs to be checked out and repaired. I think it's pretty obvious that those 4 tires are done, and for sure you want it fixed before it has a chance to eat up the next 4.
As for warranty coverage, it might be worth asking, but I very much doubt you'll get it. But ya got nothing to lose by asking.