20 days early stigma?

Typicality they say not to transplant autos but if you are gentle it will be fine. However I don't see in your diary when you transplanted them?? they always seem to be in the same airpot? I would keep them this way, that pots big enough for their lifetime. Airpots are one of the best systems I think to grow in. I want to get some for myself but my grow shops always out of them. Autos tend to show pre flower around week 4/5. Sometimes earlier, Then they will go into flower. It is true they can go into early flower from stressers like nutrients, heat or root disturbances. I don't think that's your case when checking your grow. If anything you have a solid setup and the plants look good. Best of luck and Happy Growing!