Do you know what type of azaleas they are? Are they recommended for your location/zone?

There are several reasons for lack of leaves - azalea type, watering issues (too much, too little) or pest problems. Not enough detail provided to determine what specifically.

They are Encore Azaleas, and we are about 20 miles east of Raleigh NC. We have many Encore Azaleas in the yard. These are in full sun from early afternoon until evening. Watering is on the natural watering schedule which this summer has been on the sparse side, but the problem has been there for three or four years previous. The Encore Azaleas between them as you can see is fully leafed out.

Since all three are the same variety, they all receive the same amount of water and sunlight, and it seems they would all be exposed to the same disease, I have been at a lose to figure out what that to do about them