If your front coil springs are over-loaded and being compressed, then changing them to higher-rated ones will be the simple and easy solution. I would get the rig weighed to determine how much actual weight your front springs are supporting, then compare that to the specs of the springs.
If it's appropriate, then maybe your rear is sitting too high. Maybe you are addressing the condition from the wrong end. A 24 foot rig on an E450 chassis just might be that. You might also be dealing with an exceptionally rough ride.
I changed front coil springs to softer ones to level our E350 24 foot rig. I was quite surprised how easy and safe it was to do. The first spring took over an hour, the second took only a half hour because of what was learned. Anyone handy can do it.
Done not only to level the rig, but also for a more comfortable ride. Also, it is NOT good to have so rough a ride unnecessarily. It is very hard on the structure.