|What causes black leathery spots on all my tomatoes?|
|It is probably Blossom End Rot, which can be prevented by ensuring the plants receive a steady amount of even moisture throughout the season (in other words, not alternating between very wet and very dry) and also checking and adjusting your soil to be sure the pH is such that it allows sufficient calcium for the plants.
If your soil pH is below 6, this may be the cause of your problem. You might wish to perform some basic soil tests to see if this is true. Your local County Extension office can help you with the tests and interpreting the results. Their phone number in Warren County is 623-3291.
If watering is the culprit, you can grow good tomatoes from now til the end of the season. If pH is the problem, you may be able to grow better tomatoes by using a foliar spray intended to supplement calcium on tomatoes. Good luck with your crop!