I suppose it could be either over-watering, under-watering, and/or not enough fertilizer.

However, the white-looking spots on the leaves could be spider mites and/or powdery mildew. It's kind of hard to tell without a really, really close up photo. Plus, we don't get much powdery mildew where I live, so I don't have a lot of experience diagnosing it. It's just a thought. :-)

Oh, I see you're in Texas, where it gets hotter. Much hotter. Tomatoes don't like really hot weather. They don't like cold weather either. They're divas sometimes. :-)

I think most avid tomato growers in the hot summer climates, like Texas, stop growing tomatoes in the heart of summer because the heat just devastates the plants. They usually plant early for a spring harvest, and then start early type tomatoes for an autumn harvest. So you need to consider the oppressive heat. If it's too hot the tomatoes won't thrive and they won't set fruit.

How big is the container? Tomatoes get big roots and don't do well in small containers.

Fertilize regularly, about once a week with a water-soluble fertilizer such as MG or Peter's or one of your favorites. Remove the crispy leaves.

You need something to fight the possible insect damage, and a fungicide in case that's some powdery mildew (on the greener leaves further away, maybe).

Don't provide too much water or too little water. Believe it or not, most folks tend to use too much water. Only water when the soil is completely dry when you stick your finger in the pot a couple of inches down. Tomatoes don't like to have wet feet.

I hope someone in your zone and climate can give you better answers.