keithp2012 said:
I watered daily and the spot it's in always had poor drainage, maybe that really did the older plant in the symptoms you describe do match up.
That may be the Bingo. While anything in the Rhododendron family likes soil on the moister side. They also have shallower root systems and do not like soil with poor drainage.
I would also point out the hot/drought summers of '12 & '13 stressed a lot of plants. Then the winter of '13/'14 was brutal and I think for you winter '14/'15 was even worse.
That is a lot of stress in a short period of time - particularly for an older shrub that may have been near its life expectancy anyway.
A lot of people including me lost a lot of plants, trees and shrubs over the past couple of years.
