Almost certainly Entomosporum leaf spot. You can see the teltale black spots on the older foliage as well. This is particularly difficult to control as most fungicides have little impact but pruning off any diseased material and following very good garden sanitaton (removing and destroying any fallen leaves) can help.

There is a common saying regarding these plants - there are two different kinds of photinia....those that have leaf spot and those that are about to have leaf spot :-) The issue is bad enough that photinias are often no longer sold in areas where this is common.

I've got 16 of the Fraser variety, some 18 ft tall and over 30 years in the ground... and a few in very shady sections of the yard. They benefit from sun and minimal humidity... i do get small bouts of leaf spot in shade and low branches, but they always shake it off without fungicide. I just trim out the ugly looking areas and prune to increase sun.

I love these as they are an excellent privacy shrub... and acceptable in residential landscapes. I tore out 19 100+ ft redwoods before i realized how great the photinias are. Redwoods are the scourge junk weeds in my neighborhood.

@rhizo_1 what kind of photos would you like me to post? I will also contact UCCE, but they would benefit from the same photo advice.

@gardengal48 is the fungus completely localized to the leaf, or is it in the roots?

@molewacker Are people in your neighborhood just throwing those redwoods away (probably selling off the wood to furniture makers)? Is there ever an opportunity for someone in the South Bay to buy some of those and transport to a new home? Or are they too hard to get out of the ground once the roots establish on a large tree?

Westes... only a few have a clue. Most are not thinking about the future and their neighbor's view.... until its lots of expense. The redwood roots will find your wallet eventually.