Some leaves on my well-established boxwood bushes (~15 years without a problem) have suddenly turned almost black:
This may be covered here:
(except my leaves are essentially black and it happened almost overnight...maybe within 2 days at most or I would have noticed.)
It has been really hot here in North Texas, and it's possible I have watered too much in reaction. Might anything else (e.g. pests, heat) account for this?