You can apply a liquid fertilizer that contains calcium nitrate. Add lime or calcium to your soil mix before planting your tomatoes next season. Blossom end rot can strike at any stage of fruit development. Harvest undamaged fruit when the blossom end, that facing the ground, is pink. Then allow the tomatoes to turn red indoors at room temperature.
Late blight is a fungal disease that strikes foliage and fruit.
Green to dark brown lesions will appear on the upper half of the fruit. Look for a fungicide that targets this disease. Buckeye rot usually develops where fruit touches the ground. Plant in a well-draining soil. Cage or stake tomatoes to keep fruit off the ground and to improve air circulation.