Tomato Plants Stopped Blooming?

When I planted my tomatoes it had blooms. There are 1 or 2 big green tomatoes on the plants. They stopped blooming and where the bloom should be, they've turned a blackish color. The tomatoes that are on the plants look great and are growing everyday, just no new blooms. Any information would help, what is the cause, how can I cure it?

By Kerry Jo