They are Autos they will grow under any light cycle, though 18/6 is a bit long 16/8 or close to that is the norm. You can even grow them at 12/12
If you want to switch the time on/off just switch it. A one time change in their lighting won’t effect them in any way. @Akhmilli
Welcome to the ILGM Forums! Nice little setup you’ve got there. I’m a soil grower so not much help on the setup!