A lot of maybe's and perhapsMaybe you should go down to 11/13 cycle? Perhaps try to get a bigger temperature gap between day and night time... maybe lower peak daytime temp, and drop humidity so that it rushes the nutes outta the leaves quicker... Maybe 75*F max daytime temp with 40-50% humidity, and try to get 60-65*F nighttime temp with 30-40% humiidity....
Perhaps even consider girdling.. or taking a layer of skin off the main stem at the bottom to encourage hormones for ripening, and leaching of nutrients from the leafs. Another thing is water temperature..... Warm water could perhaps loosen up some minerals and create a more rapid flow/cycling thorugh the plant in conjunction with lower but VPD safe humiidty.
I put mine back after rearranging the colas a bit. Will harvest both from the bottom on and let the upper part finish..