Give us a little more background info to rule causes. When did this problem start? What variety of rhodie is this? How old is it? How has your weather been like? What hours does it get sun? Has the amount of sunlight changed this year? Does the damage occur on leaves in the outer core of the shrub (so the inside, protected leaves are ok?) Is your soil in SF acidic or is it alkaline but amended to bring the soil pH down?

The problem started about two months ago.

The variety is Seaview Sunset.

It is about two years old.

Weather has been typical San Francisco Bay Area Mediterranean climate.

It gets sun in the morning and sits under the shade of a large tree during the middle and late hours of the day.

Sunlight has not changed.

The damage looks localized to that one limb in the photo.

The soil is redwood bark and a little turface, so it is very acidic and does not need modification.

It is worth mentioning there is a sister plant to this one and it is doing fine.

Sunburn is what I was thinking of when I hinted at damage in the outside core of leaves, the ones typically in direct contact with the sun. Fungal issues might be ruled out by inspecting a leaf with a magnifying glass. I am not quite sure just why it is localized as it is. Maybe it gets hot sun in the afternoon or evening somehow? The timing (in the summer months) makes you suspect that so keep the soil as evenly moist as you can and make random checks for sun in the afternoon or at night..

Okay, your posts got me to thinking. Pavers were installed near these plants in this time frame. The tops of the pavers were probably sprayed with some protective chemical. Now I am thinking this chemical got onto the leaves and created a chemical burn. Is this consistent with what you see?

If yes, then I guess it is one time damage. As long as it does not spread I can forget about it.

Nothing to do with any sort of chemical.

It's plain, old-fashioned sunburn. The pavers could have added reflected heat. Or not.