A: Chances are, you are doing everything correctly! Make sure the two points below are covered, and your plants should do better.
1. The plant is in a bit more sun and heat than it wants. Shrubs and ornamental trees we plant in partial shade show some strain, particularly densiformis yews, azaleas, and Japanese maples. The full morning sun is normally fine on these plants, but the unusual heat makes things difficult for them. Give your plants some temporary shade, whether by a shade cloth, a piece of burlap, a beach umbrella, or anything else that will shade them a bit more until we get to the end of September. They’ll be fine after that. And if these plants are newly planted in full afternoon sun… move them!
2. The mulch layer has worn thin or is non-existent. Keep a decent layer of mulch (anywhere from one to two inches in depth) across the top surface of your beds. It’s not just for looks! A good layer of mulch will keep the sun and wind from desiccating your soil and the top few inches of the plant’s roots. Anything covering the soil helps, but two inches of shredded wood mulch will help your plants thrive in a climate that would rather fry them in place.