Location is Portland, Oregon, USA.
We bought a house last year and "inherited" a couple of rhododendron bushes about 4 ft (1.25m) tall. One, planted in the shade of a 15' (~4.5m) magnolia, is doing very well. The other one is more exposed and gets full sun from about 1:30 PM to sunset. It has a lot of yellow leaves and some with what almost look like burned holes and edges. Below are front and back pictures of a couple of examples.
The previous owners of the house paid very little attention to the landscape so we are in the middle of a major re-landscaping project. We are hoping to keep this bush, but if it's too far gone, or planted in the wrong place, it would be better to replace it with something more appropriate.
I don't know if it's possible to diagnose it from these pictures, but any information would be helpful.