Lower leaves yellowing is not uncommon. The others look like sun scorch. Check for insects.

Looks like one of the wilts, Fusarian or Verticillum Wilt. I read that it is a fungal disease that remains in the soil indefinitely - some say 50 yrs - some say forever. Google those disease names - there's alot to know, how to diagnose it, especially about precautions you'll need to take, such as in your case, getting rid of the whole kit and kaboodle - lucky you don't have them in ground. Disinfect all tools that have come into contact with them, such as pruning tools, etc. The cause is usually too much moisture in poorly drainig soils.. Good luck!

Have you checked closely for bugs? Red spider mites in N. Tx can cause damage to plants that looks similar to this. They will be on the underside of leaves and very tiny. You may see some small webbing on the underside of the leaves too. They suck the life out of leaves causing them to turn yellow, then brown and die. I'm battling the little boogers right now using neem oil. I'm losing on a Brandywine with a dozen medium sized toms I want to harvest but need to keep the plant alive for probably 2 more weeks.

I now have this same problem!! Grrr! It was on 1 plant now on 6. In raised beds. It even jumped a bed. Last year, I had it on 1, only couple of leaves at bottom, where it starts, got rid of all leaves, it went away. But this year over night it just blew up!! My book 'Vegetable Gardener's BIBLE' By Edward C. Smith, agrees that it is one of the Wilts,Fusarium or Verticillium. He says" Control: Remove and destroy infected plants. Before the growing season begins, "solarize" soil and add additional organic matter. Rotate plants annually and plant resistant varieties."

My question is exactaly how do you "solarize" the soil?

These plants I have are my bests producers, but they threaten my cucumbers, peppers and others tomatoes. It makes me want to cry. But I do have another bed that I harvested my onions from I can replant late tomatoes in.

My question is exactly how do you "solarize" the soil?

Till soil,rake smooth and soak heavily. Put plastic down, seal around the edges with dirt to keep the heat in. Zone 8 should have no problem cooking the soil.

Solarize probably means sterilize. When I worked in a greenhouse we had a steam machine, we covered the beds with plastic and then literally injected steam. YOu can do the same with clear plastic in any sunny garden. Stake down a piece of clear plastic over anything you don;t want and it will be stone dead in a few days.

Wish I was that smart about tomatoes--I have exactly the prohlem you do and no way ouit.