how do i fix my Underworld background

[Beetlelance]

everytime I go the underworld. it has a cave background. I check my setting and my backgrounds are on. I used texture packs to see if I can change it but its still the same dark cave background.
https://imgur.com/A7cha9n

[Layal]

same issue on my end. the mods I have are:
Boss Checklist
Calamity
Calamity Music
Ore Excavator
Recipe Browser
Subworld Library
Summoners Association
The Stars Above
Unlimited Buff Slots
Wing Slots Extra

[Vssaint]

Subworld library removes the background of the underworld to make subworlds, and its required for stars above.