We have a 93 LY with rear auto leveling suspension. If pressure is ok On the dash air guage but the coach still sets low first thing I would check is the two air leveling valves one on each side somewere on the undercariage. I cant tell you were because ours is single axel not tandum.
They take air from the accunuliator and eather fill, exhaust or stop air flow to raise, lower or hold the rear end. They work by an input shaft that moves up or down movement of the part of the coach that sets on top of the rear air bags. They may need adjustment, or as it was in my case they were both leaking air arround the input shaft to each valve. I could level it and come back the next day at the same time and had 40 to 45 Lbs. If you dont have a leak and try to adjust them to bring the coach back up to 10 to 10 1/2 " bear in mind that each valve has a 3 to 10 second delay built in so make small adjustments. If you have need of it I can send you a diagram of the airbag system, just PM me with an email add.