Can i increase daylight from 18 to 20 hrs in autoflowers?

As long as you aren’t organic yes you can but light distance requires to be adjusted (raised) as well. In organic grow dark is important because it is during such time that plant stores the sugar it produces via photosynthesis in the soil

Most definitely! Autos can be ran on 24 hours light. I actually prefer to run 20/4 I've had my best results with autos grown under that light cycle. Rest/night hours are important for a plant. So I give em 4 instead of running 24 hours. Love it. Happy growing and stay lit fam.

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