The spindliiness sounds like an issue of how they got started. Did you start these from seed yourself or buy them as transplants?
They may have been a little leggy starting out, from too much heat/ not enough light. Starting the seedlings it helps to put a fan on them sometimes or shake the plants a little. Being moved around as they would be naturally outdoors, helps sturdy up the stems. Also when you plant tomatoes, you should always plant them deeper than they were in the pot. They will develop more roots all along the buried stem, which makes them healthier. If you didn't do that, you still can - don't dig them up at this point, but hill them up a bit, bury the bottom part of the stem.