Hi MSWolf, I also have a White Plastic Birdbath in my yard. I clean it with a bathroom bleach cleaner and rinse it off with the hose for about two minutes. The feeders also need to be cleaned at least once a week, remove all seed and wash off, let thoroughly dry before refilling. Hope this helps. A lot depends on when you put up your feeder.
Hummingbirds are very territorial, and they often pick their territory early in the season.
If you just put up your feeder in the last month or so, it may be hard to lure the local hummers away from their already established home turf. However, young hummmers are just starting to fledge, and most hummers will begin migrating soon. Keep your feeder up, because you may attract those young birds who don't have territory of their own, or hummingbirds moving through your area on migration. Next year, mark your calendar to put up your feeders a week or so before hummingbirds are expected in your region. I can help you figure that out, if you like.