That's an easy one, very distinctive. It is not a disease, it is a little insect larva called a leaf miner, that gets in between the layers of the leaf and burrows through it, eating leaf tissue and leaving those trails.
Because it is inside the leaf, it is not very susceptible to sprays. Easiest thing to do is at the first sign of squiggles, just remove and destroy (not in compost pile) the leaf. Hopefully if you catch it before the infestation gets so bad, you won't be defoliating your plant in the process.
In the meantime the plant can lose a fair amount of leaf tissue that way without suffering too much, so it's by far not the worst problem you could have.
For future reference, there's a wildflower called velvetleaf, that makes a great trap crop for them. It has very soft velvety leaves (hence the name) that the miners prefer to anything else. Grow a few of those and keep picking the squiggly leaves off them. I discovered that by accident. I planted a packet of mixed wildflower seeds. All the rest of the stuff died out, but the velvetleaf kept reseeding itself. So that would be a way you could obtain it.
If you don't remove and destroy the squiggled leaves, the larva eventually matures, leaves the leaf and drops down to the ground, pupates for awhile, and then metamorphosizes into a tiny fly like critter, that lays eggs inside more leaves (250 or so at a time). In favorable conditions the whole life cycle can occur in about a month, so they can multiply rapidly, as you have seen.
Since you have so many of them right now, another thing you can do is lay down plastic mulch under your plants, to help prevent the larvae from reaching the ground to pupate.
In the meantime, the healthier and more vigorous your plants, the less they will suffer from the tissue lost to miners. Are those plants growing in containers? As near as I can tell from the pics, the plants look crowded into small containers.
This is turning in to more than you wanted to know about leaf miners
, but one more thing. Have you been using general insecticides in your garden? Sometimes when you see an outbreak of leaf miners like this, it is because the garden was sprayed with insecticide, which removed the beneficial insects that would otherwise help keep the leaf miners in check (tiny parasitic wasps and others).