Sagging rear end on 1988 420SEL

[Timmy2]

Good morning! I'm the proud new owner of a 1988 420SEL. Seems generally to be in decent shape - pretty low mileage (about 75k on the clock) & pretty well maintained over all. Rear suspension is spring and shock absorber. Shocks aren't leaking and seem to be ok. Driving around town the car feels a little squishy and loose to me (but this is my first Mercedes so maybe that's just the ride?), but at highway speed this thing is solid like a rock. Amazing.

But the rear end looks low to me - like maybe 1-2 inches. I have zero experience specifically with Mercedes, so I need some help here.

My first suspect is those bushings that connect the differential / final drive to the rear sub-frame. There appear to be two. What do you guys think of this?

And / or maybe at 30+ years the springs are tired? But why only the rears?

I look forward to whatever thoughts / advice anybody wants to offer!

Thanks.