It sounds to me like the one in distress was not planted properly. It may have root strangulation from not being root pruned when planted. It may have a dry root ball because the root ball was dry when planted. It may be in a less than desirable location due to something strange in the soil. Sometimes it take a number of years before strangulation becomes evident.

I would recommend digging it up and examining the roots. If they are strangling themselves, prune them so that the offending stranglers are removed. If the root ball is light from being dry, soak in a bucket of water a couple hours before replanting. Examine the original hole. It it looks OK, well drained and not soggy or too dry, then just put in some new conifer bark and peat with the native soil.

When digging, remember that the roots are very shallow and extend out to the drip line.

Here is a link that might be useful: How to care for rhododendrons

Thanks for advice. Right now it is next to a small flower bed with some special perennials in it which would be seriously distressed if I dug up the rhody in a way to get all roots (even though plants are not under it, they are close - and they are not big water/nutrien hogs - smaller plants for the most part). Can I cut rhody way back and dig it in the fall? How far back? And don't you think it's strange that it flowers so well even when leaves look droopy and are so sparse?

Two things - This bush has been there for years and just keeps getting more spindly each season. The soil in this bed is great for perennials so I don't think it's soil. Probably what you said about whoever first planted it then?

Deborah

You don't need to get ALL the roots to successfully transplant a Rhody.....if the other normal transplanting procedures are followed. You do not need to cut it back to transplant it. Water well after transplanting into a proper medium in light shade out of the wind. Sometimes, too big of a rootball is a handicap. I've transplanted hundreds and hundreds over the years as a Landscape Contractor with 30 plus years experience. My busiest time was spring all the way through summer.
I'm being blunt and mentioning some credentials in the hopes of dispelling some preconceived notions when it comes to transplanting rhododendrons.
Mike...retired, but still working in my garden. See below.

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