If you have over 50 hours and have not changed your hydraulic fluids and filters, then something like that might be a good first step.
If you think it's more mechanical than hydraulic in nature.... On my Exmark... made by Toro... there are set screws just under the plastic beauty panels to make the adjustments at the extreme limits of lever travel. In the mid-lever positions there are adjusters on the struts running to the hydraulic units.
Hope this helps.