I went to the html sandbox, and looked at your pic..well, I copied the url into my browser & looked. Yes, definitely leafminers. Cut those leaves off, and throw them away (don't compost them). If possible put some kind of mulch, like plastic around your plants, so when the pupae that are in the dirt try to hatch, they can't escape...or get some of those yellow sticky paper traps. If you look closely on your leaves, and see a stipple/pimple looking thing, that is where a fly has deposited eggs into the leaf.
If it's a light infestation, and the tomatoes are healthy, they will still produce, but eventually those leafminers take their toll on a plant because it weakens the plant.
BTW, the offending flies are yellow and black, and about 1/8 inch long. I think I've seen them and thought they were some kind of tiny bee.
Thanks X3. I read up on them last night, but the mulch idea is news. I used grass clippings last year. I’ve got some of the rubber mulch & will use that. (Like the fly strips, too)
Last year, the plants looked awful but produced like crazy. This year’s plants seem a lot happier.
I’ve seen the little devils. I thought they were baby wasps.