this thing happens frequently
I think it should possible to restrict the cave fog under a specific y level
I know about caves above y ocean level, if you think about the sky shouldn't be dark even from dark place
this happens too while whatching trought a window inside a close space
So, that's my suggestion soemthing to restrict it

Thank you so much, I'll wait for the next release, I love your mod so much

fixed in version 1.1!