Is it possible that your plants were exposed to herbicides? If you put weed and feed on your lawn and it came into the garden via rainwater, that will cause deformation of the leaves and stunted growth. Make sure you don’t use treated grass clippings in your lawn or compost pile either.

Use an organic fungicide based on Bacillus subtilis as described in the article.

Sounds like classic blossom end rot. It’s not a disease but rather a physiological disorder caused by a lack of calcium in the growing fruit. Calcium can only get into the plant with water, so while there’s likely plenty of calcium in your soil, it can’t get into the plant due most often to inconsistent watering. Tomatoes must be watered very deeply and be kept consistently moist. The plants should not be allowed to completely dry out between watreings. Dig down into the soil after you water and the moisture should go down at least 5 inches into the soil. If it doesn’t, you need to water more deeply.

Is it possible that you have cutworms in your soil? They sometimes chew around the exterior of the stems at soil level. Also, be sure to keep your mulch from touching the stem. It could hold excess moisture against the stem and cause rot.

Hi Patrick – Sounds like it might be a varietal issue. Beefsteak-type tomatoes often drop several flowers from each cluster, allowing only one to remain and form a single large fruit. It is also possible that the flowers are not being pollinated properly. Tomato blossoms are self-fertile, but they need to be “buzzed” by bumblebees (or strong wind or plant movement) in order for the pollen to be knocked loose. If you don’t have enough bumblebees around, you could try holding an electric toothbrush on the flower stem, just beneath the bloom. Hold it there for about three to five seconds. That’s enough to knock the pollen loose and fertilize the flower. Mimics the buzz pollination of bumblebees.