I do not think the damage is snails or slugs as they tend to eat from the leaf margin and leave some slime behind. Instead look for a small green "worm" or larvae from a moth or butterfly. You may need to go out at night with a flashlight to catch the culprit in the act. If you have just a few plants you can handpick the worms. If you have a large display of inpatients there are some insecticides with Bt or Bacillus thungbergia that are beneficial nematodes that will destroy the larvae. The good news is you can wait a few weeks and see if the problem goes away on its own. Sometimes the larvae turns into an adult and flies away.  Keep growing, Marianne Binetti