The coarse webbing and browning suggests that there was a species of tent caterpillar that previously hatched and fed. Prune out the affected area, if possible.

The leaf just above the browned area appears impacted by spider mites or a leafminer. If you have a hand lens, take a look at the leaves and search for microscopic insects. Alternatively, hold a piece of white paper beneath the affected leaves. Shake the leaves to try and dislodge insects on them. If you see black or yellow looking specks walking on the leaves, these would be spider mites. A horticultural oil or insecticidal soap controls mites. Here's a resource on the types of leaf damage caused by spider mites: https://extension.umn.edu/yard-and-garden-insects/spider-mites#:~:text=Damage%20caused%20by%20spider%20mites,underside%20of%20leaves%20and%20needles.&text=This%20injury%20produces%20tiny%20white,and%20has%20a%20yellowed%20discoloration.&text=On%20azalea%2C%20leaves%20and%20flowers%20also%20get%20distorted.

The remaining leaves that are discolored are probably due to insect feeding as well, but I'm not sure who is to blame.