Janet wrote:
Hebes have in recent years been suffering from a nasty fungal disease,
Do you mean, those horrible spreading black spots on leaves? Some of
ours have been plagued with that in recent years. Picking off affected
leaves seems to slow the spread but is a PITA. It's only some varieties;
the hebes with large leaves and large bottlebrush flowers.

Is it at all related to the rose black spot fungus, do you know?
(and hence, treatable* with black spot spray)

* not that I've found it very effective!