I bought 3 similar plants from Lowe's: 2 Better boys and I Cherokee Purple about a month ago. They were about 1.5' tall and all three plants were very similar. They all had a lots of flowers, were about the same size. Now both BB have half a dozen fruits on them (the largest about an inch in diameter) but almost did not grow, CP on the other hand grew like crazy but does not have fruits and no more flowers. All are Bonnie Plants brand in the same containers with obviously the sale soil. I did not feed them since I assume Bonnie Plants provided first initial feeding at the factory. What is the reason for CP not to set fruit and flowers?

Old beefsteak tomatoes will generally just drop their flowers if conditions are not ideal (plant energy). I can assume at 1.5 ft tall these were not robust plants but rather lanky, so that round of flowers was lost. Then it became overly vegetative, it will indeed produce later, but these tend to be strong and long cropping plants, so it's not all bad.