I would chose the Osmocote Indoor/Outdoor formula for your plumeria, zingiber and other houseplants. As for your mystery plants, Zingiber is a Ginger plant from the tropics so it likes a moist, humid area with well drained soil - don't let the pot sit in drainage water. It is an adaptable plant but will do best in bright light - just keep it away from cold drafts and cold windows. This is not the same species as the ginger plant that gives us the spice or root called ginger - so don't try to eat it! Sounds like you've got a bit of Hawaii in your home with both plumeria and ginger - Aloha, Marianne Binetti