Weird tomato problem

I have one tomato plant that is growing in a different container from all the other ones. They're next to each other, and same type of soil, but the "lonely" one is in a bed twice as deep as the other one (so I thought it would do better than the other ones). In the rest of this deeper bed I have aubergines and peppers, that have done wonderfully. However, the fruits on the tomato plants are extremely tough. The get to the size and deep red of a mature tomato, but they stay so hard that they're basically not edible. If left on the plant, they eventually start to "wrinkle" as tomatoes do when they're way past their prime, but inside they're still hard. The same variety on the other bed has produced a ton of lovely tomatoes.
Has anybody had this problem? Maybe it's just a bad plant (I suppose that heirloom plants can go wrong sometimes), or could it be that being surrounded by aubergines is not good for tomatoes?

What's the variety?