Posting one additional photo. The problem initially presents as leaf wilting/curling before the rust color damage.

I have advised that this problem may be fire blight.

Fire blight is primarily a problem of apples, pears, quinces and a number of species in the roseacea family. I've never heard of it infecting any rhodoendron/azalea species. Further, fire blight makes the effected leaves look as if they had been torched. They are black, not the brown color seen in the photos.

There are, however, several fungal diseases which do effect azaleas and produce the damage shown in the photos. Your County Extension service or state agriculture department are the best places to give you more specific analysis and advice.

Could be a root problem.
Have you checked for the moisture content of the soil?

Curious jean001a whether the soil issue you mention is too much water retention and root rot? In my case, I was seeing wilting in two of my five new plants that i set into freshly relined holes ( topsoil with peat/humus mixed in to compensate for rocky clay subsoil around foundation) . At first i thought the plants were not being kept moist enough and the leaves wilting from lack of water. Top layer of soil was dry. However, despite daily watering, two of five plants have started to shutdown and I fear I will be pulling them in a week or two.
See pictures....

A slightly more advanced problem in this second plant. If this is a leaf fungus problem I can give them a spray with the copper solution I use for my peonies.