Yep, your lighting is plenty good enough so its not that.
Its possible you've got a weird one, Ive got 4 Dark Devils flowering nicely but there are some of the strangest growth patterns ever, Ive got really deformed leaves on two of the four plants, as soon as I can get my head round uploading photos I'll post some.
Leaves with 3, 4, 5 and 7 fingers. totally asymmetrical, it has to be a result of the way the breeders are messing with the plants genetics.
Auto flowering in Indicas and Sativas is not natural as far as I know.
Whenever we change the natural order it causes so many variables, from what I have read, very few of these autos are ready for harvest in the time stated by the breeder.
They can be taller, smaller, quicker, slower and all from the same strain.
Ive got 4 plants and I would now say I have 3 phenotypes.
These autos are a bit different to photo strains so yeah, I reckon there is a good chance you just got yourself a retard there, a bit 'care in the community' like.
Unless its taking up needed space you may as well just hang on and see what happens, use it as an experiment.
Good luck mate.