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Unfortunately, these are not deer resistant. However, you could try placing deer-resistant plants around the perimeter of your home or even protect the shrub with a cage. Deer usually steer clear of any plant that is fuzzy or prickly, extremely aromatic, or excessively tall or short. This article may help: https://www.gardeningknowhow.com/plant-problems/pests/deer/deer-repellents.htm

Photinia is very susceptible to the fungus leaf spot, called Entomosporium, that can defoliate photinia plants. Plant photiniain full sun and provide good air circulation. Remove and destroy fallen leaves, prune off diseased twigs. Avoid overhead irrigation. Fungicide sprays (copper-based products) are also generally necessary for this disease, beginning from bud break and applied every ten to fourteen days until all foliage has matured. Mature foliage is no longer susceptible to infection. Not sure if this is the problem (wouldn't be water issue as the others are seemingly ok), but treating with fungicide wouldn't hurt. It may actually help prevent it from spreading to the other shrubs if it is in fact a fungal issue.

Treat the plant with neem oil. It is both a fungicide and a pesticide. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm

What is the pattern to the plant turning brown (i.e. bottom up, all over, etc) and how old are the plants? This will help us determine what this issue might be.

Is your soil alkaline? That's a common cause of chlorosis in photinia. Try adding some sulfur to the soil.

The following article should be of some help to you (towards the end): https://www.gardeningknowhow.com/ornamental/shrubs/photinia/growing-red-tip-photinia.htm