To clarify: I water my tomatoes on every third day for 20 seconds each. The one with leaf curl is slightly overwatered, probably because I have so many adjacent plants that I've been watering every day.

While they are deep rooting, tomatoes also have lateral roots that aren't very deep, but grow long.

The soil they are in is native clay mixed with sheep poop + some compost. They're high beds, about a foot tall, which is great for water retention and overall plant happiness.