I'd be more inclined to say genetic. Not that I know for sure but I've got a seed line I created last year that exhibits this trait in about 10-15% of the offspring.
Summittoker,
Did you get that JF as a clone? That looks exactly like the one I used to make my seeds. Would be nice to get that back again as she's some superb smoke. At least I think so.
I have an Iranian Male doing this right now
So to be clear you have a seed line that exhibits fasciation in 10-15% of the plants? Were the parents both fasciated? So you have or have seen male fasciated plants?
-SamS