Its an auto.
There is no set time for when they flip pal.
& without a diary. Its hard to tell what caused it. If it was genetic, or caused by stress. (If u moved to a bigger pot etc) these things should be avoided when autos leave seedlings they need to be undisturbed in the substrate
Add a diary.
Autos are a gamble. Its y you should have more than 1. Especially doing your 1st grow.
I suggest, while u learn.
If u want a quick turn around..
Get a F1 fem. Then u control the flip. And flowering can be 7-10weeks, depending..and you'll get much bigger plants.
Make a diary
GL