SharePoint Calendar Overlay Permissions - users have full control.

Hi SP community,

I have setup multiple calendars each with their own overlays. Each overlayed calendar has its own unique permissions per calendar owner - the owners have "full control" permissions. I originally setup the calendar but now I want to empower the team to be able to create/edit their own calendar. Even with full control they cannot edit, rename overlays, restructure in general, etc. How do I enable them to be able to edit their calendars?