I offer no answer but am kindred in your concern. The Cedars in my yard are displaying the same symptoms as yours. Not just one but all the Cedars on the property, most would classify as old growth. From top to bottom, rusty discoloration on the tips of the branches. You could have taken that photo from my yard. Oddly, this is also a new phenonoma for our trees, never noticed before. I wonder if this is some kind of blight. I refuse to ascribe “global warming” as we’ve had the same consistent crappy weather as always.