Do you know what variety of rhododendron you have? If you do, then you can figure out if they’re of a variety that prefers more shade or more sun. It sounds like your plants are growing quite well, though, so it may be the case that they simply need more time to establish themselves. Rhododendrons can take several years to truly settle in, at which point you should see better blooms. Another thing to check is that they are not drying out too much. Adding mulch (but leaving space around the trunk to prevent rot) can help with that.
Do you know what variety of rhododendron you have? If you do, then you can figure out if they’re of a variety that prefers more shade or more sun. It sounds like your plants are growing quite well, though, so it may be the case that they simply need more time to establish themselves. Rhododendrons can take several years to truly settle in, at which point you should see better blooms. Another thing to check is that they are not drying out too much. Adding mulch (but leaving space around the trunk to prevent rot) can help with that.