The interesting thing to me is that Long Island where Keith lives had far more than average snowfall the past couple of winters, which one would have assumed would protect the azalea more from cold than previously. Then again there would have been a lot of snow to melt, plus Long Island had some major flooding from rain in the summer of 2014. Whether Keith's specific area was affected by these events I don't know.
Looking at the picture of the base of the plant raises a few questions in my mind. Firstly there are several branches that have been cut off. I'm wondering over what time frame, is this all in the past two years or has it actually been declining longer? A couple of branches are hollow. One cut branch has some staining on the cut surface although it doesn't seem to be around the cambium as far as I can see.
Anyway, if there's a chance Phytophthora could be involved, and we're not likely to know for sure without a pathologist examination, there are lists of replacement plants that are less or not susceptible, such as this one:
https://plantpathology.ces.ncs...
