Certified GKH Gardening Expert
This is a fungal infection from severe overwatering. At this point, they will likely not make it, but you can make an attempt at correction with fungicides:
Thanks for the reply. They are probably 4 feet tall but have never been watered. Up against my garden fence, with the street pavement on the other side. Puzzling that they prospered to get to this height over a few years then fell ill. I'll look into the fungicides.
Will the location just be a poor one for them?