Looking at some of the JD pages I'm thinking I'm due for a new hydraulic drain, new filter and even a seal on the mid PTO shaft where the mower shaft attaches.  I'm trying to figure out how long it's been which means it's been too long.  A burned PTO clutch, plugged hydraulic system, etc. can cause some of what I am seeing I guess.  I should say it isn't bad on how it cuts, just feels like the discharge used to be faster/harder and as I've said before about the engine increasing in speed.