Why do my tomatoes look like they’re rotting?

Blossom end rot

Blossom end rot is caused by a lack of calcium in the growing fruit, and when this deficiency is solved, the afflicted plant can continue to thrive and produce perfect fruit later in the season. This condition is most seen in tomatoes, but also found in capsicum, chilli, squash, eggplant, cucumbers, and other fruiting plants.

What are the symptoms of blossom ...