Why are my photinia’s leaves having partial discoloration?
Certified GKH Gardening Expert: I believe this to be a fungus that is common to the Photinia. Here is a link that will help you: https://www.gardeningknowhow.com/ornamental/shrubs/photinia/growing-red-tip-photinia.htm https://www.gardeningknowhow.com/ornamental/shrubs/photinia/photinia-leaf-spot.htm. I would agree with that but if you notice it isn't leaf spots, this is what makes me leary about it being a fungus. Any other ideas?
I'm still fairly certain your dealing with a fungus.
Here are a few more links.