It is calcium deficiency but pulverizing egg shells won't solve the problem fast enough, since they'll still have to be decomposed further before being available to plants.
Either use a specific tomato fertiliser, or better still : manage your watering better, as it is often the real cause.
One possible solution to calcium deficiency: Pulverize egg shells and work into the soil around the plants.
It is calcium deficiency but pulverizing egg shells won't solve the problem fast enough, since they'll still have to be decomposed further before being available to plants.
Either use a specific tomato fertiliser, or better still : manage your watering better, as it is often the real cause.