Was getting very little hot water out my dual element 240volt WH... drained it, clean out sentiment, inspected elements I had put in a year ago - OK. When refilled & plugged in I put a tester on the elements & noticed only 120 volts on bottom element. Is this normal or should the bottom element be rated for 120volts? Or is this a miss wiring issue?

Your only reading 120 volts at the heating element because there is a thermostat above it that only switches one leg of the 240 volts.

Here is a thread I found in Plumbing that has various wiring diagrams showing how a thermostat and element is wired.

https://www.askmehelpdesk.com/plumbing/show-me-diagram-electric-hot-water-heater-425399.html