tomato bottoms turning black!  and bumps on the stem

tomato bottoms turning black! and bumps on the stem

Photobucket i have amish paste tomatoes planted both in my garden and in pots. some of the tomatoes on the plants in pots are turning brown on the bottom. i've never seen this before, and its not happening to the ones in my garden. can anyone tell me what is causing this and how to stop it? also happening to the tomato plants in the pots are bumps along the stem. what are they? Photobucket bumps on stem: Photobucket Photobucket EDITED TO ADD: blossom end rot! off to the garden center tomorrow in search of ways to add calcium. thanks everyone!
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