I don't pretend to know the answer for sure, but I know that endogenous [The plant's natural rhythms. Search endogenous and/or circadian] factors exert a considerable amount of control over the growth of many plants. With the onset of short days (after the summer solstice) a large fraction of plants stop extending and change their growth habit from multiplicative (increasing the number of leaves and branches) to additive, during which they grow axially, or get fatter. Many tropical trees (but not limited to only tropicals) exhibit episodic growth, during which they grow in spurts, and then 'rest' awhile before the onset of the next growth episode.

If it's not related to genetics or day length, it's cultural. Since root growth always precedes top growth, if your top isn't growing you should be thinking about the roots. Actually, you should be thinking more about the roots anyway, because the top ain't gonna be able to do much w/o root support. What might you have going on in the root zone that inhibits root function? Compaction? Root congestion? Over-watering/excessive water retention? Inappropriate nutritional supplementation? How about the light the plant is getting?

Al