This is what I noticed for damage I don't see any holes or anything like something an insect would make so I think your probably right about it being a mutation. It just looks like it grew into a split on both sides of the stem. Thank you for your time and help. Is there anything I could do to help or should I just let it do it's thing.
I had a feeling it was due to some sort of damage.. I have to agree with the bent over/snapped theory. Usually these things heal themselves relatively quickly, thus the bulging. You can maybe help it heal a little faster by applying aloe gel to that split, but not a whole lot you can do at this point. I would just leave it be and keep doing what you do.
I've actually saved more broken branches and stalks by simply not touching them, than trying to fix them. The remaining woody vessels inside the stem and branches tend to swell and take over the job of the broken ones, so minimizing movement, I've found, helps a lot.
You could try staking the plant if you notice it's swaying a lot more than the others.
I still stand by root zone issues if you're seeing a very big difference in growth between this plant and the others - the soil looked really saturated in those pics, as far as I could tell.
Could you give us a basic breakdown of your entire setup?
Feeding/watering schedule, ppm/pH of food, etc.
Soil type?
Nutes used?