Tie the top shoots down now! You don't have any other option if the plants are too tall for your space and you're already flowering... it's too late to trim them back and if you can't raise the light or lower the plants you have to tie them back.
Get some good staking points either on the plant containers or in the tray and pull down the tallest shoots until they are at a managable canopy level. They will revert back to top growth and be pointing up a few hours after tying them down. You won't get the big huge top colas but you will likely increase your yield.
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