Various creatures can cause holes in rhodies. The last photo shows extensive root weevil damage which is very common in this area. But tends to be primarily cosmetic with rhodies planted in the ground. Some cultivars are highly attractive to these pests; others far less so.

Not having grown significantly in five years would indicate some issues with planting and/or aftercare. Too much shade, too deep, insufficient water, lack of necessary nutrients, etc. And plants that are stressed for any of these reasons will be much more prone or vulnerable to insect damage as well.

Weevils are often worse under low branching evergreen trees or building overhangs. In your pictures it looks like your plants have been placed in such a situation. They would do better with more access to light and with direct exposure to rainfall.

fwiw, rhododendrons are one of the easiest things to transplant... they have shallow roots and don't mind being moved, especially when they're small like yours.