Germanoanswered grow question 5 years ago hey, you have to options
Wait for like 2 weeks more
or change to 12-12 ,your other plants will be ok but they will get less Light,which means less yield at the end
your second question ,if your plant goes into flowering after switching to 12-12 ,it will reveg if you go back to 18-6
so if i were you,i would wait couple weeks more before switching light and stress them ,hope this helps you