I bet they are Leafhopper nymphs. I'm having a terrible time with them on the Lamiaceae (Mint) family plants, especially.

Looks like a serious case of downy mildew and some cobweb situation....spider mites or regular spiders, I have no clue. I'd cut them down to the ground like Ken suggested. Depending on where you are, if it's warm enough -- it might just grow back before the winter.... Or, if it were my plant, I'm more likely to pull them out. Mint is too common to come by or to grow from a simple grocery store cutting to have to raise this one again come spring. Rhizo - is this any better for you?

If there are translucent flecks in the leaves, then I think it is most likely insect damage. Spider mites, maybe? The only things that bother my thyme are leafhoppers. They cause those sap-sucked flecks, but they fly all over the place when I touch the plant so I feel as though you would have noticed them if they were present. Variegated leaves can burn easily in the sun, but it will not cause the flecking. If you're sure that it's spread to your other herbs, then I don't think it's a disease. The only diseases likely to affect all four of the plants you mentioned are those caused by Rhizoctonia solani and the water moulds. You would be seeing the symptoms develop rapidly stem-by-stem, and they'd involve heavy leaf loss or wilting. If you've got healthy leaves and damaged leaves on the same stem then it is unlikely to be one of those diseases.

I'm pretty sure the white bugs are actually the skins of leafhopper nymphs, left behind when they advanced to the next stage of their life cycle. They are not likely to be the cause of the leaf loss, though. I'm pretty sure that is natural: as the stems get longer, the lower leaves will drop. The rate of leaf loss depends on a number of things, but you should prune it back to some of the lower nodes to encourage it to branch out.