Why do my tomato plant fruits start to rot and fall the ground. The leaves are yellowish and rotten.
Tomato Fruit Rotten
Certified GKH Gardening Expert
This can happen for many, many reasons. It may have wilt, blight or another common tomato disease (https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-diseases.htm).
It could just be that the plants are not getting enough water. Without enough water, they will let the fruit die to try to save itself.