Good Morning Deb, 

Thank you for contacting the U of M Extension Service. 

Please click on the following link about azalea problems: https://extension.umd.edu/resource/azaleas-and-rhododendrons-identify-and-manage-problems/  You can click on each specific disease and get the details of the disease. 

My first thought, as yours, was to test the soil as your azalea needs a lowerI pH in the soil than most garden plants.  You might consider if the trees have grown up around the plant and given it much more shade, or sun than in the past?   I agree the leaves do not look healthy. 

Here is another possibility; azalea sawflies: https://extension.umn.edu/yard-and-garden-insects/sawflies#azalea-sawfly-1041960

I would inspect your plant up close to view the damage. Are the leaves dead and brown, or have they been eaten by an insect?  I would also inspect the branches and the soil around the base. 

Good Luck!