Miriam C. wrote: These tires were bought at a garage sale (devorce) from a person who raced go carts or something. They were new.
These aren't race compound tires are they? If so, the rubber is so soft that they are lucky to last 200 miles (even new).
I'd consider checking the alignment to make sure the axle isn't bent. You can check the alignment using the tape measure and string method. It's not laser accurate but accurate enough for a trailer.
I don't think inflation problems would show up in 200 miles. I had mine at around 23psi for the trip to Cedar Creek, it was about 380mi and I still have the fuzzies on my tires.
Worst case, you will have to get a new axle. Since it is a leaf spring axle (I think) it won't cost very much.