Recommend: Replace all 4 x leaf spring packs to "+1 next size up". If one upgrades +2 sizes up, it can create too much stiffness. This stiffness is then passed to its leaf spring brackets and/or tires. For my many trailers (RV, boat, utility), I always +1 up size - when that suspension item wears out and/or needs breakage replacement. And when tires (rubber) needs replacement, do investigate their +1 size up as well. This works for me...
Remember: Many trailer factories build to "minimum" standards. Building higher than minimum costs dollars (which is profits from their pockets). Minimum standard = higher risk of broken parts. +1 up size and reduce the risk of breakage...