Thanks for your response! I'll not give up on them just yet! I do have a feeling that they aren't in a good spot. We sweep snow on them all winter and also they can get a bit of salt on the rare times that we salt the steps. The dying branch progressed from the outside in.
I've not watered them ever and they seemed fine until this year. I'm guessing they are about 15 yrs old, so maybe it's an age thing.
in spite of my neglect, they seemed fine until this year.