Certified GKH Gardening Expert
They may get just a little too much water. You will want to make sure that the top couple of inches has time to dry out, completely, between waterings. Instead of compensating for the heat by watering more, try a shade cloth for the hottest part of the afternoon.
This article will help you to grow tomatoes to their potential:
This link will take you to a free ebook that you can download on the subject of tomatoes: