Photinias are usually trouble-free, but can suffer from photinia leaf spot. This is considered to be a physiological problem (i.e. not caused by any pest or disease). The purple-brown spotting on the foliage is typical of a plant under stress. Recently planted semi-mature specimens are particularly prone, though many photinias are not fully hardy in the UK and any can suffer after cold, wet winters.
To avoid this type of damage plant in a sheltered spot preferably against a wall or fence. Cold winds and/or frosty conditions can also damage foliage, again causing leaf spotting if adverse conditions are prolonged.
Feeding with a general-purpose fertiliser such as Vitax Q4 or Growmore in spring or early summer should encourage healthy re-growth. Photinias respond well to pruning so thinning out some of the top growth on badly affected plants will also encourage younger, more vigorous growth later in the season. If the ground is heavy incorporate organic matter to aid with drainage.
Purple blotching can also sometimes be a symptom of powdery mildew on photinia.
Fireblight is more serious, but is unlikely to affect P. × fraseri cultivars such as 'Red Robin'. Occasionally, P. villosa and P. davidiana are affected.