u/Alternative-Ad-8389

I've had a hard time pinning down what is happening with my tomato plants. Many of the lower leaves get this browning that seems to propagate from within the plant but the actual damage looks like mites perhaps or a fungus? You can see some squash plants beneath doing fine. Image 3 is up close under a 5500K light.

My first instinct was some kind of soil issue but this area is heavily composted with kitchen scrap homemade compost so that seems unlikely. Open to suggestions.

Central Texas - 9B / 10A zone