That is from a bug called a leaf miner. You can get some pesticide dust for that. If it is just a few leaves you can pick the leaves and destroy them. They will slow the growth of the plant.

Snails and/or slugs. That's what those white trails are. Save your egg shells and sprinkle the crushed shells around the base of the plants. It will keep the snails and slugs away as they get cut by the sharp edges.

difficult aspect seek on to google or bing that can assist