Is it possible the environment available in the Octopot caused it?
Sure (IMHO), especially if that thing doesn't have any kind of air pump or other active aeration device in its reservoir. But it could be something else entirely, there's lots of random stress everyday - and some of it is in regards to plants .
It may simply be a phenotype expression we haven’t yet witnessed.
Entirely possible, I suppose. But was this a "store-bought" DDA seed, or one of the many selfed seeds that all came from the same production run using only one parent? If the latter, I wouldn't necessarily expect to see much in the way of variety in the... ah... variety. Minor differences, yeah, like this one grew to 64" and that one grew to 67" under the same conditions. But for something that's probably (if it even is a genetic trait in the first place) going to have to be the result of getting a pair of recessive genes in order to produce the trait, you'd sort of want to have a more normal mommy and daddy type activity, lol, instead of one parent having to donate all the genetic material. Unless that parent had a pair of the recessive genes in question instead of just one (if it didn't have any, it wouldn't be possible regardless of whether the seed production was via sexual or asexual means) - in which case I'd expect to see the trait in every child plant.
A random mutation is always a possibility, but the odds are pretty low compared to a symptom of some kind of stress. Could even be something that the gardener wasn't aware of, especially if the stress was relatively mild but chronic in nature as opposed to something "harsher" that was a single event instead of repeating or occurring over a longer period of time. And, yes, especially if the plant is, otherwise, a healthy and productive one.
Remember, though, just because I'm smart enough not to chug my plant nutrients doesn't mean I'm a qualified phytologist.