Q.suffering 21 yr. old daphne
What would cause my thriving 21 yr old Daphne to suddenly lose leaves. So far it seems to be only partially but I had a similar instance with one (approx. 8-10 yrs old) that lost leaves slowly until it was completely “bald” and died several months later. Never could figure out what happened.

Certified GKH Gardening Expert
Apparently it is unusual for a daphne to live as long as yours has! Here's a quote from our expert:
"Another potential problem with daphne is that it is known to die suddenly and seemingly without cause. Because of this tendency, you should think of it as a temporary plant. Place the shrub in areas where you can easily remove and replace it as it becomes necessary."
Here's a link for the article: https://www.gardeningknowhow.com/ornamental/shrubs/winter-daphne/daphne-plant-types.htm