Q.Dying photinia
I planted 9 dwarf photinia 12 months ago. Started by digging a trench a filling it with a soil and general compost mix. The leaves on 7 of them have recently gone all red and the photinias seem to be dying. They are exposed and are planted alongside a pavement and road (see photo). Can you advise what will have caused this problem and whether there is anything I can do to save the plants. Many thanks

This is the natural coloring and leaf progression for the Red Tip Photinia shrub.
Here is an article to refresh you on the care of this shrub.
https://www.gardeningknowhow.com/ornamental/shrubs/photinia/growing-red-tip-photinia.htm