Answer: Since you say the plant looks healthy otherwise, I wonder if it is getting enough water? Is the entire root system getting thoroughly soaked? Pots very quickly dry out in the desert and usually need to be watered daily as temperatures warm. Also, pots heat up to very high temperatures, especially if they are sitting on hardscape patio surfaces. Put a 2 inch layer of mulch on top of the soil to help maintain soil moisture and reduce soil temps.
Tomatoes are also subject to a variety of diseases, such as fusarium or verticillum wilt, but the leaves would also be yellowing and browning. The best way to prevent these diseases is to plant resistant varieties, which will have the letters F or V after the variety name. Finally, fertilizing will probably not improve wilting since wilt is not usually a sign of nutrient deficiency.
Q&A Library Searching Tips