Q.tomatos
have grown tomatoes in the same place for over a decade, very good soil, always return plants to soil after season , fertilize organically, and use miracle grow time release granules sparingly. Last year I didn’t have the bumper crop I usually do , but was fair. I use Bonnie plants purchased from Wal-M….. I did not find this problem addressed in common problems on internet. Please advise .

This is blossom end rot.
Here is an article that will help you.
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm
I would encourage you to use crop rotation in your garden.
Every 3 years is the recommendation, to avoid soil born diseases.
Here are some more articles that you may find informative.
https://www.gardeningknowhow.com/edible/vegetables/vgen/rotating-vegetables.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/growing-tomatoes-guide.htm
https://www.gardeningknowhow.com/edible/vegetables/tomato/tips-for-growing-tomatoes.htm