System has been loosing about 1 litre of hydraulic fluid per month although there is no visible leakage in the rear near the accumulators or the shocks. There appears to be some spotting on the driveway where the front of the car is usually parked.
Recently the rear drivers side has been riding lower than the passenger side and when the car is loaded and turning right it sounds as if there is something grazing the tire. This situation appears to be deteriorating as the car requires less loading to make the same sound when turning or going over a speed hump.
Where would be the logical place to start looking without throwing parts at it?

Site search did turn up a few possible culprits, from differential mounts to bad accumulator, but i'm not certain that they may apply in this case. Suspension does not feel unduly harsh, nor bouncy. The fluid loss has been an issue since i purchased the car 2 years ago, albeit the rate of loss has slowly crept up over time from ½ liter to about a full litre per month.

Any suggestions as to what else can be checked to narrow down the troubleshooting process would be appreciated.

TIA
Patrick