Welcome to the world of unpredictable auto flowers!
18/6 would be much better for your plants, no plant has ever evolved on Planet Earth to grow under continuous light.
Pants do need "sleep" and thrashing them with never ending light is very unnatural.
Cannabis plants can only grow so much in any 24 hour period and this growth tops out at around 18 hours, meaning running your lights any longer than 18 hours, is basically a waste of electricity. 18/6 was derived at through 80+ years of research into cannabis and is not a random number.
Occurrences like what you are having was part of the reason I stopped growing autos for ever. Not much you can do anymore, once they start flowering, that's it.
She will maybe double in size, maybe only a third more, but not much more, and yes, they do need bulk light to perform to their best.
Hope this helps,..........
Organoman.