Tomatoes have really taken off with the warm weather. Remember blossom end rot, especially with the uneven moisture conditions we have been experiencing. While blossom end rot is technically a calcium deficiency, it is really caused by uneven moisture supply to take the calcium around the plant. Mulching with 2-4 inches of material will greatly help your situation later at fruit set. If you are watering, use an inch a week. This amount, combined with mulching, should be more than adequate.