Black Spot on Bottom of Tomato on Plant

Question

I have a pot on my deck, approximately 12″ W X 13″ D. The tomatoes are about the size of a golf ball and smaller. They are above the ground 3 feet or more. They have a black spot on the bottom which gets bigger and softer, looks like rot. I water them regularly and use Miracle-Grow every 2 weeks. What can I do to prevent this, or is it too late? Please advise.
Thanks
Bill

Answer 1

this may help:
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm
and this one too:
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-diseases.htm