This is quite typical for Hostas by midsummer, and reflects some heat stress, slug or insect chewing, and a degree of anthracnose infection. You can inspect the foliage upper and lower surfaces, especially after dark, to see if slugs/snails or beetles are present and chewing holes. Neither seriously impacts the health of the plant, though can make leaves an eyesore. Make sure the plants are being monitored for watering needs during our ongoing drought. (The linked page focuses on watering trees and shrubs, but largely applies to perennials as well.) There is no fungicide we would recommend for anthracnose, but pruning off individual leaves with leaf spot and yellowing may reduce the spread of an infection, and remove all spent leaves later this autumn once they are killed by frost so they don't harbor spores over the winter.

Miri