Answer: Tomato plants, like any plant that produces fruit, need at least seven hours of direct sun. If you have less, you will have fantastic foliage but very few fruit. Fruit production takes a tremendous amount of energy, and tomato plants, like all plants, get that energy from the sun. If you can move your plants to a sunnier site, the fruit should ripen quickly.
The problem you describe with brown spots on the bottom of the fruit is called blossom end rot. It is common, and is related to inconsistent soil moisture. Keep the plants well watered - When the soil around tomato plants dries out, a serious problem results. Calcium, one of the handful of minerals needed by all plants to grow, is absorbed by the plant's roots along with water. If water is limited, so is calcium. The result is blossom-end rot, a brown, dry, leathery spot found on the bottom of fruit. So make sure your soils don't dry out and use mulch to help conserve moisture.
Celebrity is a determinate variety. It will grow to a maximum size, set fruit and then stop producing. Indeterminate tomato types will continue to grow and set fruit until frost arrives.
Q&A Library Searching Tips