Have autos in flower so should I just switch to 12&12 light or stay with 18&6
Stick with 18/6 for an auto. It will help ensure that the plant’s DLI requirements are met.
You don’t have to switch to 12/12 with autos, you can continue with 18/6 all the way. 12/12 would save you some electricity costs, just keep DLI in mind like mentioned above.
If your interested in DLI
What is dli
DLI = Daily Light Integral. Read Nickys post, the top that @Dave101 shared