I have a b6200hst. Rear tires (29x12.00-15) worked fine, but were dry rotted everywhere. Finally I found a used Goodyear turf tires 29x12.50-15 to replace them. they looked newish. Had them mounted. A day or two later both were flat. Filled them back to 10psi. the rims look nice from the exterior. I’ve heard sometimes you need a bead sealer, or an additive, etc. I’m assuming the guy who installed would have looked for rust. Ideas from here? Thx