Name: Lynda Horn Arkansas (Zone 7b) Eat more tomatoes!
I think that the yellowing leaves are normal. And the plants look very good! Can you possibly transplant to some larger pots and keep them inside until it's warm enough to plant outside? You could start over, but they look so healthy I would try to keep these going and growing.
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa