Looks like an insect of some kind, maybe spider mites.

I hadn't even thought of that! Here's another photo from another plant. I have neem oil, is there anything else I should be treating it with?

That along with B a y e r Fruit Critus and Vegetable Insect control. It is a systemic solution that you water into the soil. That along with giving your plants a good spray and wash with a mixture of dishwashing liquid to water will also help or just water. You can also use your neem oil. I would also use what I suggested above to help systemically. It looks somewhat like an aphid and spider mite infestation Hope this helps.

Thanks so much! I'll give it a try.

Here's some info on common tomato diseases in FL & some remedies as well....

Here is a link that might be useful: tomato diseases

Thanks!

I also found this guy today on another plant (he's yellow on the top part of the leaf). Is it a baby horned caterpillar? I have noticed really tiny little holes in the leaves too.

No one told me this many bugs loved tomato plants...sigh.

The little tiny holes are caused by Flea Beetles

Just a quick update - I've been spraying regularly with insecticidal soap (Dr. Bronners + oil + water) and neem oil and my plants are doing great! I keep killing the white flies that like my brandywine, but other than that everything is healthy again.

I also started planting my newer plants in containers (instead of terrible FL soil) and dang, they're growing like gangbusters! I'm very excited!

Thanks for your help!