The fruit on my containered tomato plants is rippening and most own a big brown/black spot on the bottom.?
Yes, it's blosson-end rot, a adjectives symptom of calcium deficiency that is brought more adjectives when there's inconsistend watering.
This happens rather habitually, even in greenhouses on the first fruits on a tree. Pluck the tomatoes off and hope the rest of the yield is better.
You have blossom extension rot. It's common with tomatoes that own had inconsistent watering. The inconsistent watering causes a calcium fewer in the plant.
Ways to remedy: (1) Water more consistently. (2) Next time you make thorny boiled eggs, save a couple of the egg shells and crumble them up and put on the soil. Boiling the eggs before foot takes salmonella out of the picture.
Gypsum can replace calcium but before accumulation gypsum or lime, you should have your soil tested. The pH of your soil dictates which you would add.
Answers: What you have is called "blossom-end rot". Your soil is low contained by calcium, try adding some gypsum to the soil. Once you have mixed the gypsum into the soil -- wet it in thoroughly. Good luck.