Not sure where you're located, but how wet has it been?

South Carolina, the ground is always wet about 6 inches below surface level

No hibiscus expert here for sure. maybe they are just shedding some old leaves.

are you seeing shriveling in the branches? yellow leaves - not a huge issue by itself, but the stem change, means rot or too much water, likely both. tropical hibiscus don't like constant wet feet. I get really concerned when the budding leaves start dying.

I have found if the leaves are yellow towards the bottom of the plant, its may be being over watered.