New York City is mentioned in the post.
I also think they are too close to the masonry there and I wonder what is beneath the soil and what was left behind. I am guessing there is a foundation under the stonework. I would have the soil tested. Japanese holly like conditions on the acidic side and maybe because of the stonework, the spot is alkaline. Contact your local extension center for a soil test.
Also, we had two years of high temps and droughty summers. That did one of my Japanese shrubs in after having it for many years. Yours had additional heat reflected/conducted from the stonework.
A lot of broadleaf evergreens do prefer more acidic conditions so maybe at least plant it a few feet from the masonry if you have the room. Yews are more tolerant of a range of PH.
Cornel Cooperative Extension - New York City - 212 340 2910, supposedly they have locations in the 5 boroughs.
https://cals.cornell.edu/corne...
