I can not assess the health of the plants in these photos but the gray, greenish white stuff looks like lichen. That is harmless to the plants.
A lichen is a symbiotic relationship between a fungus and an algae. They are growing on your bushes just for support. They are not feeding on your plants. I find lichens to be some of the coolest things on Earth.
But from your images I see overgrown plants in need of a good prune. Perhaps they have been neglected for years. Dense and tangled plants could be killing themselves by not allowing for good healthy growth by blocking light penetration.
But they are suffering perhaps but it is not because of the lichens.
