As a general rule more light = faster growth you just don't want to drop below 14 hrs of light imo to be safe.
Also there's Defoliation as an Option. When you remove leaves from your marijuana plant, you are taking away energy it put into vegetative growth. This will cause your marijuana to slow down growing, especially if you remove a lot of leaves. In the vegetative stage it is used to control the growth and structure of your plant. Basically leaves removed from any “branch” during the vegetative stage causes that branch to grow more slowly.
Hope these suggestions are helpful. Happy Growing! 👊