Looks like the little trails thrips leave behind. Do you have any patches of spotting on any of your leaves? Either way I'd at least start off with some neem oil or anything with spinosad in it. I tried Monterey garden insect spray, and it seemed to work really well, although after a month or so they always seem to come back. I've also heard that their larvae can hide under the soil so I've been using mosquito dunks in the soil. I'm not sure if it's helping with my thrip problem, but it sure knocked the fungus gnats out cold! Good luck bro, they're some tough little creatures.