Thank you for your question.
Most tomato fruit problems are caused by irregular watering. Examples include 'Blossom End Rot' (dark patch at the base of the fruit, more common if the plant is grown in a grow bag), 'Blossom Drop' (flower bud falls off), 'Dry Set' (fruitlet growth stops when the fruit is the size of a match-head), and 'Fruit Splitting'.
The key is to give your tomatoes an even, regular amount of water at the base of the plant. Too much water too late tends to be the problem in most cases, especially with plants grown in pots and grow bags.
Other problems tend to be caused by too much direct sunlight. Tomatoes need high light intensity to grow well, but too much can cause blotches, scalds or spots on the developing fruit. 'Greenback' is a common problem caused by too much sunlight, leaving the ripe fruit with a hard green area on its ‘shoulder’. If this is a problem increase the potassium in the plants' feeding regime and use fleece or shading as a cover in the hottest part of the day. It may also help to use resistant varieties such as ‘Alicante’ or ‘Craigella’.
I will put an Hub together when I get the chance. Check direct sunlight and in terms of what I recommend growing Fruit Trees are ideal.