m0useanswered grow question 2 years ago The changes of the plants being photoperiod is there and its very low. I don't think you would see that one two of the same plants from a single seedpack but who knows.
I think if you let them go a little bit longer it should be ok, Autos are not known for having the most stable genetics in the industry. sometimes they just grow different then there sisters/brothers and that's from poor breeding or a few select phenotype of the strain. There are other things that can shock an auto inot early flower as well like to many nutrients, transplanting or other root zone disturbances. Given the amount of mixing that's happening with autos I have seen them take 7+ weeks to go into flower, buddies of mine had one for 9 weeks then it switched into flower. It was a fast buds mexican airlines kinda nuts it took so long but it did switch on its own under 18/6.
That being said I would not switch to 12/12 and leave it as is.
Best Of Luck!