I think it's this mod that makes the health and food bars look like gems.
https://www.curseforge.com/minecraft/mc-mods/quest-plaques

I'm not sure which mod would need to update for this.
AHilyard/QuestPlaques#6

The extra hearts are on top of the first health bar like normal, but I think they should be gems to match.
Just, well, gems of a different colour. Like how the second health bar is orange hearts.
To match, they should be orange gems.

The overlaying hearts display is not part of our mod. You're likely using Mantle, which is mostly a library mod but also performs this change.