When snails or slugs go for Neps they leave large holes and major chunks are removed from the leaves. This happens overnight. Definitely nasty blighters. Snail/slug bait with wheat gluten and iron based (not toxic to other critters) should take care of the problem. You could try a jar lid full of beer. The nasty blighters go for the beer and end up drowning and dying. A little messy to dispose of... but what a way to go.