Conor Sipe wrote:
The leaves (which were looking a healthy dark green when they burst
forth
from their buds) have begun to turn a silvery color.

Disclaimer: I know nothing about bougies. But I do know silvery
leaves. You should check for mites and thrips, either of which can
cause a stipply, pointilistic silvering of leaves. Mites can be tapped
onto a white sheet of paper; thrips can be hard to find- they like to
hide in leaf folds and crevices. I can recognise either of them from
their frass, or excretia (sigh. Like I'm *bragging* about this).

Ozone, other air pollutants and pesticide damage can cause a silvering
of leaves, but I'm guessing that's not your problem.

Nina. Frass expert.