Busting slugs snacking on cabbages
It still could be slugs and snails, as some feed at night. However if it is cabbages, they are very prone to caterpillar attack, especially from cabbage whites and the eggs might have been laid before you put your netting over. I would suggest sprinkling some Advanced Slug Killer Pellets on the ground around the plants to kill any slugs or snails present. For the caterpillars, I suggest you closely examine the plants for signs of caterpillars, if there are some there still. I suggest Insect Killer Spray containing Pyrethrum. This kills on contact but is safe to use on edible plants. Both products are available from Harrod Horticultural.
Next year I suggest getting Netting over them early and early applications of the Advanced slug killer product. I hope this helps.