My tomatoes are turning brown from the bottom up. What to do??

That is called blossom-end rot. It is caused by a lack of calcium. A handful of lime in the hole when you plant them is best preventative. Obviously, it is too late for that, but you can try incorporating some in the soil now. Be sure to water it in well. That may help.

are the leaves touching the ground, I have always been told to clip off the bottom two leaves when the plant is growing it releases the nutrients so the plant will grow larger and bush out more and in turn usually will produce more

It is blossom end rot... however there are several reasons for its cause. Inconsistent watering is the easiest to fix- set a pattern for your watering, don't over water then let dry out completely. Next is lack of calcium. Yes, you can add lime however you may alter the soil pH too much, so try a liquid calcium supplement, they also have on the market preparations made specifically to "end blossom rot". For plants long term needs, try crushing eggshells to a powder and tossing them around the plants.

Jaweb. 🍅

Also don't let any leaves touch the ground, that's how it gets transmitted. Crushed egg shells have worked great for me.

I think epsom salt and vinegar mix and spray and it will get rid of most bugs and brown leaves and will help them to grow

http://www.gardeners.com/how-to/blossom-end-rot/5354.html

There is no problem with the fruit, its only the vine and I think I discovered the cause this afternoon. There is an armadillo maturing around out there at night and I think he is breaking branches off just below the ground