Check the tires FIRST...especially with this much difference. It is not the psi that matters, it is the circumference around the tire. with the back of the mower lifted, use a soft tape measure (like the tailors use), or even a string or something. Also, id the tires are that low, both should probably be inflated a little more. It may even help the cut quality due to changing the deck pitch. After the tires are dialed in, they can be adjusted by just adding or taking out air from the tires. Very seldomly is it a hydro adjustment that needs adjusting.
Thank you, Dad - for always being the dad that you were. You truly are my hero. You always were.