In optimizing gear for power and toughness, the pink and rainbow hearts are assigned to my loadout even though I can't get them -- I haven't beaten Godmother yet. The gray, pink, and rainbow hearts should be locked until "Highest Zone" is at or beyond the appropriate titan.
You can actually get the rainbow heart before Godmother through one of the mtx packs.
I'd suggest you simply disable (right-click -> disable) the hearts though.
In optimizing gear for power and toughness, the pink and rainbow hearts are assigned to my loadout even though I can't get them -- I haven't beaten Godmother yet. The gray, pink, and rainbow hearts should be locked until "Highest Zone" is at or beyond the appropriate titan.