For sure, something is not happening right. Your plants at 4 months should be BIG and bushy and have flowers and small tomatoes on them.
You say they are getting almost full sun and in decent soil and fertilized. That leaves me wondering about weather conditions and water. I know you said "great drainage," but sometimes that is hard to tell. The commonest thing that would cause that kind of stunting would be that the roots are waterlogged. If there's too much water around the roots, they can't get oxygen and can't uptake nutrients. If that persists, the roots will rot.
I would dig one of the in ground ones up (you don't have much to lose, if they haven't done anything by now, they aren't likely to), gently, digging up a dirt ball with it, so you don't break the roots off. Shake or gently wash the dirt off the roots and see what is going on. Also check the dirt in the hole you left, see how wet it is. The roots should be extensive, well branched, firm and white. If not, you have located your problem.