Answer: How frustrating! Since you see that tell-tale slime, it is probably slugs. They work at night which would explain why you haven't seen any. You can hand pick them at night by flashlight (barbecue tongs work well!), set out traps baited with beer, or sprinkle diatomaceous earth around the plants to control them. There are also some newer less toxic baits on the market such as Sluggo and Escargo. Salt can build up in the soil so it is better to try another method.
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