That's a lot of plant for that pot. They need moisture.

And consider light shade during the heat of the day.

{{gwi:1292219}}

For what it is worth since I don't "do" containers:

Most people who grow tomatoes in containers would not really consider anything less than 5 gallons (look at some of the "earthtainer" threads). Even with 5 gallons of soil, the plants transpire so much that they need to be watered thoroughly at least once a day when it is hot. Twice when very hot.

Those poor babies look like they almost need to be watered hourly.

Bets

I yet again agree with bets. ;) More water and, if possible at this stage, a bigger pot. Fertilize with a water-based solution also, if you haven't yet. Other than that, the maters look nice!