Thank you for reaching out. 

We would need better photos of the leaves when the symptoms first appear and are not already brown, shriveled and dead. 

This time in the season many tomatoes are struggling from the heat and drought of the summer and have succumbed to Septoria, late blight, mite damage, etc. Mites were a struggle for many tomato growers this season with our high temperatures. 

There isn't anything you can do not for the plants so we would just recommend getting the fruit you can from it and discarding the plants at the end of the season. 

If you have a photo with a new symptom on the leaves you can try to send in some of those and we can try to pinpoint a cause to the dying leaves but it may be too late in the season to know what it is for sure. 

Emily

Hi Jon, 

We think this is end of the season septoria and early blight symptoms. They are difficult to control but make sure to clean up all the plant debris and spent fruit at the end of the season and discard. 

You can try watering at the base of the plants if that's an option in your community garden. Also remove the bottom 3-4 branches to let air flow through the plant. Next year thing them out and make sure they have good air flow between the plants and also their own foliage. 

Emily

you're welcome!