Hi Anthony,
Sorry for the late response, I have been away for Xmas.
I'm always trying to remind folks that any structural deformation is always a result of poor CO2 since Carbon is the main ingredient in structure.
As usual, this always presents us with a puzzle because we may observe that other plants do well in the vicinity and so it is tempting to stray from the path and to look for other causes, but rest assured this is a CO2 issue. Different plants have different strengths and weaknesses, so it is entirely possible that this is a weaker, less efficient specimen than the plants surrounding it, or, that it is such a fast grower that it requires more CO2 than the other slower growing plants. The usual solutions are to be considered, i.e., injection rate increase, light reduction, increased Liquid carbon dosing and so forth, each with it's advantages and disadvantages. You may also wish to consider moving the plant to a different location to see if the mean CO2 levels (or flow) are better at that location. You can also try to prune in order to see if the new leaves are better adapted. Place the cutting in an open area to see if it does better there.
Same story here. Slow growth, once lack of nutrients (PO4 especially) are eliminated as a possible root cause, can only be a CO2 issue.
Again, you can try moving the stem around to see how it responds.
The problems in a CO2 tank never get any easier, they only get trickier...
Cheers,