The shortest one is maybe a foot tall, but already has 3 tomatoes on it, 1 of which I had to get rid of due to a bite missing from it. I know these plants are supposed to get to about 9' in height, which is why I'm a little concerned at the seeming lack of growth. Should I be worried and try to do something, or should I just wait and watch?

I live in NC, and the weather since I have planted my garden has been.... unusual. A week of cold and rain, then a week of warmth and sun. Now a week of warmth and rain.

Were both varieties from the same source? Without knowing the complete facts about the plants you have, at best we are guessing....

And now I'll go out on a limb and make a guess:

Did the Cherokee Purple have fruit on it when you planted it? If so, that could be the reason it isn't growing as fast as the Brandywines. Instead of putting its energy into root and plant growth after transplanting, it is trying to produce fruit at the expense of the overall plant growth. This is one reason you will usually see advice to remove blossoms and fruit from a tomato plant when you transplant them.

Betsy

The size of the plant is determined by its genetics in addition to the growing conditions. So IF you insure they are both given the same growing conditions then it is the genetics of the variety that make the difference. CP never reaches 9 feet, maybe 6 feet. It is normally a smaller plant than BW even at full growth.

Dave