If you haven't already, check the plants at night, because often insects that chew leaves feed after dark. Primary culprits may be caterpillars (for the ferns in particular) and beetles like Asiatic Garden Beetle, which is notorious for feeding at night and disappearing during the day.

You don't need to intervene as the plants should regrow normally next spring (it's fine if they don't produce much new foliage this late in the growing season), but if you did take action, your only options are to either catch the insects in the act of feeding and pick them off, to cover the plants with insect mesh to block access, or to spray the plants (only if there is enough foliage left) with an insecticide using the active ingredient spinosad, which primarily targets chewing insects. It is absorbed into leaves, which the insect then needs to ingest to be exposed to the pesticide. They stop feeding soon after, and die withing a few days. If you opt for that method, read and follow all product label directions, but it should be the choice of last resort since the affected plants should be fine.

Miri

You're welcome!