My first guess is rabbits. Slugs or snails will also devour an entire leaf but they leave a bit of slime behind. Of course deer and some dogs can also eat entire leaves but rabbits are the most common culprit. You might try sprinkling the foliage with red pepper flakes. Sometimes that will deter dogs and rabbits. A good fence or nylon netting over the plants will also make they less likely to disappear. Keep growing, Marianne Binetti