96 Maxima is "bottoming out"

Ive got a 96 maxima GXE 228,000 miles running great mechanically. I just replaced the water pump, pvc, spark plugs and fuel filter.

My problem is whenver I go over speed bumps, pot holes, or small animals (kidding about the last one). It feels like the car bottoms out completely.

So what do I replace? The shocks, the springs, both?

Any feedback would be appreciated.