Yep, blossom end rot.

More often than a lack of calcium in the soil, is uneven watering which results in an inadequate supply of calcium carried all the way to the end of the line -- namely, to the fruits.

On the Growing Tomatoes forum click on the FAQ button and review the discussion on blossom end rot. As jean says it can often be prevented and eliminated by controlling watering and avoiding high nitrogen fertilizing but air temps also play a role.

However,
one plant that is eaten up with BER, that the leaves are getting spots on them, then slowly curling upward and eventually turning yellow, but never seem to actually die.

The leaf problem is NOT a symptom of BER and BER is not contagious. You may have some early blight going (can't tell from the leaf pics) from soil splash onto the leaves or if you are overhead watering it MAY be the early stage of a fungus. Or it could simply be a case of leaf roll.

If you can post a better pic of the leaf problems, yellowing, etc. it would help distinguish between all the possibles. ;)

Dave

Hi and thanks for the help! I will try to get a good picture of the leaves sometime tomorrow, as it is already getting dark here and would be hard to get a good one. I was afraid of Blight.. if I find one tomato with the bottom rotting then in the days following ones off the same "cluster" will rot as well, which is why I thought it seemed contagious. Plus it has slowly moved down the line from plant to plant, with my first plant in the line being the worst. Thanks again!

Also I've found out that the more the plant grows the less it puts into the fruit, less means less calcium, which means BER. This is due to too much Nitrogen in the soil.