if your moss is drying out over night then your humidity is WAY too low. I have moss on all my vandas bec they were drying out too fast. Not potted in moss just a moss topcoat to keep the top fresh. Indoors I never had luck with the vanda types. Was not sunny ,hot humid and stikky enough for them IMO.
But good luck on your endeavor to grow these under lights.
They do much better in the greenhouse. Even spanish moss grow on them.. I love moss!!!