There are a number of threads about bent axles and flat springs and this was a warranty issue back in 2013 from what I read in the forum. Leaf springs are always supposed to be curved. Once they are flat when under load or permanently deformed unloaded they no longer are able to do their job. My suggestion is to replace axles, springs, mounting hardware, and if need be, all the rest.
It's true that subtracting the trailer tongue weight helps a little, but not much. When you are traveling down the road at 45 mph or more and the trailer bounces around, the dynamic load on the suspension can significantly overload the system. Do a search in the forum "axles" or "springs" . I've included a few of the many links. Hope you get it resolved soon!
https://www.jaycoowners.com/forums/f...ems-91263.html
https://www.jaycoowners.com/forums/f...ems-72077.html
https://www.jaycoowners.com/forums/f...ted-15137.html