If you have photinias in your established landscape and they are healthy, you may want to leave them but if you see the maroon speckled leaves, you may want to consider removing the diseased shrubs. After the terrible winter in the early 80’s, wax leaf ligustrums froze to the ground and many of us turned to red tip photinias as replacements. They were over planted and the disease started to devastate this species. We had many of them in our landscape and some of them have since been removed because of the disease but we still have ten that are beautiful and the size of small trees. I cannot tell you why some died and some have survived and flourished that is just the way it is in nature.
Gardeners are sometimes concerned when a plant develops a disease that it will spread throughout their garden. Most diseases are species specific and will not bother another type of plant even when they are planted in the same area.
So my recommendation to you is to evaluate your photinias in your landscape and if you like them and they are healthy, enjoy them.