Posted: 08/01/2014 at 18:21
Not sure. Photinias all seem to have spots on them from time to time and regularly lose a lot of leaves, in my experience.
I lost one red robin to phytopthora.....a separate comdition I'm sure. I have another that has black, brown spots ESP during the winter. In spring the new growth however transforms the bush. So I wouldn't worry too much if your plant generally looks healthy.
Early summer I prune lightly to encourage a further flush of red leaves and this tends to remove most of the tatty old leaves