The bearings in one of the wheels was spewing grease all over the rims. They didn’t look rusted out, but I guess the seal failed or we must have gotten some water in there and it expanded on the drive home.
My brother in law knows a guy, who rebuilds cars and trailers, and he was willing to take a look. $400 later we had brand new bearings on all four wheels and the surge brakes and lines were all checked and maintained. He also cleaned it all up, now with the new bunks, the trailer is looking pretty good! (I wish I remembered to take a pic)