There are holes in the leaves of my hosta plants and Montana plant
from past experience. I think you might have a problem with slugs or snails, hostas are "fine dining" for slugs especially if you have varieties with variegated coloring. Apparently the lighter colors are quite tender and easier for the pests to munch on. There are commercial products (slug pellets)to spread around and under the plants, crushed eggshells. You need quite a few, and diatomaceous earth. Have used all with varying degrees of success.