Filters. Which hyd , drive hyd, or implement hyd such as loader, 3pt, etc.
Install a pressure age and monitor the pressure and report back. Maybe the pump is worn, and is pumping less than advertised, with low pressure.
A relief valve could be held open by debris/trash.
If you take your tractor by the dealer, and have them do a flow and pressure test, they can give you an informed idea what may be wrong.
Check that the 3pt lever is not all the way up, and keeping the system in relief.