Brown spots on Azalea
We notice insect damage on the leaves. Right photo - left leaf looks like feeding by the azalea leafminer and some surface feeding on the middle and right leaves.
No treatment is recommended now. You can rake any fallen leaves in the fall.
Look for mines in the foliage and feeding damage next season in May. Larvae feed in leaf mines and in curled leaves. If you notice this, you can treat with spinosad.
See more on our website https://extension.umd.edu/learn/ipm-series-azaleas-and-rhododendrons-hg51