Q.My Tomatoes Were Doing Great Until Recently. The Leaves Are Turning Yellow & Curling.
I don’t if it’s the heat we are experiencing in Texas or not. My garden is in large tubs sitting on bricks. I’ve been watering every other day & dont water unless the soil feels dry. The fruit all looks good. I notice no mildew. I have 14 plants. Not all are turning g yellow but all are very wilted. As can be seen my peppers are wilted also. After dark all but the tomatoes perk back up.

Certified GKH Gardening Expert
It could be the heat. The curling is a defense mechanism. It also could be uneven watering. These articles should help pinpoint the cause:
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-leaves-curling.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/wilting-tomato-plants.htm