We did have frost damage on the Kitsap Peninsula from a freakish early frost that went from 60’s to 25 degrees in one day back in Nov. of 2014. And lots of it did not show up until now (April) but I do not think this is frost damage although being a former Californian I’m no expert. Looks like disease. Is it Sudden Oak Death? Photo attached. It’s affected half the Arbutus unedo Compacta very suddenly, that’s for sure. And we have LOTS of rhodys. If it is, bummer, because it occupies a key corner of the garden.
Maybe root rot or honey fungus - it will probably be something at the root rather than sudden oak death, which would be best identified by a lab.
