I have noticed many Coprosmas (including mine ) that have blighted leaves and stems. It doesn't seem to kill them but only disfigure them. It almost looks like foliar Phytophthora on bedding vinca. Has anyone else figured out what it is and how to treat it?

Can you post some photos? A wider overview of the plants and some close ups?

While generally advertised as "trouble free", Coprosma is susceptible to mites (very susceptible actually) and root rot in less than perfectly draining soils.

It's well possible you are dealing with one of these two problems, but without further data is kinda hard to know.

Here's some pics of one at work (Pomona) in half-day sun, slightly sandy clay loam, watered 3 times a week.


This is mine in a pot with coarse Cactus Mix, about half-day sun and watered 3 times a week.




Most of the damage at work is in the interior, but it happens on outside branches as well. The smaller one at home shows mostly smaller branches, but they also coalesce into whole branches.
As you have said, they are known as mostly disease- and pest-free, but this keeps happening.

I think your problem is the cactus mix: unless it's really good stuff it generally keeps too much moisture and/or is too heavy because it uses construction-grade river sand.

If you stick your finger in the pot all the way, how's the moisture? Does the sand in it sticks to your finger or can you blow it off?

Not much sand in the mix, lots of perlite with coarse organic stuff and fairly fine sand. I don't think soil is the issue since it happens in most any type. I was hoping someone would have dealt with it before and know some kind of treatment.