I recently noticed a few gnats and added some mosquito bits to the water which I use to water it with... not sure if it is related though.
It looks like edema-related damage to me, considering the bumps and yellow spots. It can cause leaves to sort of shrivel like that, too, in my experience. There are probably flecks without chlorophyll visible when you hold a leaf up to a light. These can turn into round (sometimes yellow) bumps when the plant gets wet/humid (and remain round bumps).
To remedy the problem,
- don't stress about it too much (edema is primarily a cosmetic problem); a virus, on the other hand (if your plants are infected with one) may be cause for stress.
- reduce humidity
- reduce heat (if the heat is causing humidity)
- make sure plants aren't close together
- add some air circulation (e.g. a fan; this can dry things out more)
- avoid getting water on the leaves
- Giving the plants some potassium/calcium may help their structural integrity. In my experience, it seems to reduce the edema problem, too.
You don't necessarily have to do all of those things, but each should help with edema.
Even if a virus is present, the plants do have edema. I don't personally know that a virus is present, but Bamboo might know something I don't about what is in the picture. Maybe the curling leaves, or the uneven veins are the sign there. The vein issue may be due to a calcium issue; sometimes viruses look like deficiencies and vice versa.
Air circulation should help to reduce fungus, and keep the leaves and the top of the soil dry. I'm thinking it'll reduce the gnats.
Humidity and heat can be good for fast growth in plants, but it can also encourage edema.
Edema can be a bigger issue if you have mite issues, or some such.
If you take the steps I outlined above and the problem, sans the bumps, still exists on new growth, then it's probably a virus or something like that, and you should probably try to figure out where it came from. Viruses don't usually appear out of thin air. Fungal and bacterial infections, and even pests are more likely to seemingly come out of nowhere. Pests can spread viruses, as can contact with infected material (i.e. infected plants, soil from infected plants, things made out of infected plants, insect hosts, things or people that have touched infected plants and such, containers that had infected soil in them at one time, etc.) However, they won't just appear in poor conditions without a vector.
Your plant looks as if its acquired a viral infection, for which I'm afraid there is no treatment. More information can be found here: Tomato viruses. If you have no other tomato plants then you can risk waiting until it becomes even worse to make sure it is viral, or simply dispose of the plant now.