It might be insects chewing the leaves, but it could also be slugs/snails. Any pest you do not see actively feeding won't be affected by a pesticide that is relatively safe for use on plants visited by pollinators; they have to be present to be impacted by the spray. (Plus, slugs/snails won't be affected by an insecticide.) Try checking the plant at different times of day - mainly morning or evening, when it's cooler, or after dark - and keep an eye on the leaf undersides as well. Some leaf-chewers only feed at particular times of day and move away to hide the rest of the time.

For now, you can snip off the worst of the chewed leaves, not only to minimize minor secondary infections and improve the plants' appearance, but also to make it easier to detect fresh damage. It's possible natural predators have discovered the pest(s) and have eaten them already, so if you don't see new damage, no treatments will be necessary. If you see something you suspect is the pest but need it identified, feel free to send us photos.

Miri