Patching and Plastering - Overcut Holes in Plaster Ceiling - What is safe to fix?

Well, after adding some 4" shower IC housings for a new shower's lighting I put the wet rated trims on and realized they don't quite cover the holes cut for these fixtures. Bummer, i thought I was pretty precise considering it was plaster.

My question is what is safe to fill in these holes since whatever I use to fill will likely contact the light housing and get warm, as well as damp from the shower. The gaps are small (1/4" or so), but the little trims I have just didn't quite cover them.

Caulk? Drywall compund?

Don't use joint compound - it's water soluable!

Is this a painted wall/ceiling that you cut the holes in?

Both caulking and a setting compound like durabond should work. If this is around tile - use grout or caulking.

Yes, it's a painted plaster ceiling in a shower. So a setting type joint compound would be okay with both the heat and moisture?

I wouldn't expect any problem with the heat from either durabond or caulk. They will be ok without paint but would likely look better painted :D
Joint compound might be ok once painted but you are relying solely on the paint to protect the j/c.