25% of established rhodo has drooping leaves
I've a rather older rhododendron in my garden that has been never well, but improving in health every year since I moved here as I've fertilized it and deadheaded it (or so I assumed). This year it had the most blooms ever (I've been here 7 years) and I thought it's bad days were over - but then about 25% of its leaves began to droop extremely badly - and the rest have never looked so good. The blooms on the rest of the plant are now all open, with the ones on the drooping branches not.
I've looked for insect bites (the borer), but not seen anything. I've read about root rot or roots that are too dry - but cannot dig it up to check as it is rather immense. Should I cut off the drooping branches? The leaves are still green after weeks of drooping (in case this is of use.) Thanks for your advice.