I was having the same problem with lots of wasps and big bees on one of my feeders, but no bees or wasps at all on the other two Hummzinger feeders. They are supposed to be good at keeping bees and wasps from being able to feed. From my limited experience, I would say it's true.

I have heard that you can move the feeders that the bees found and that the hummers will find them right away and it might take the bees days to find it. Try to move those feeders somewhere else and see what happens.

What kind of feeders are they? I would also rinse the outside of the feeders and be real careful when filling and hanging the feeders not to shake any sugar water out on the outside of the feeder.

I use hot soapy water and sponge for cleaning my first nature feeders, [no it does not deter hummer from using it at least not at my place] just rinse them well with cold water. Before hanging feeders I try wipe or remove any possible spilled liquid from outside the containers. I have a hummzinger excel which is supposed to be bee proof but wasps still hang out on it. Maybe its swinging in the breeze sloshes some out I just cant believe hummers are that sloppy.

Another trick you might wanna try is make one feeder extra sweet and hang it away from your good hummer feeders and hopefully your bees will find it.

Some hummingbird feeders have feeding ports with bee guards on them to keep them away. If your particular feeder does not have that option you are really out of luck. Hummers will not feed if the bees are there.