Add a wet towel. Higher your light and turn up the % of the light.
This will increase heat from light, but will also increase ppfd so be sure to move it above 60. Use a phototone app.. get the lux at the current hight and then you'll have something to go from by moving the light up and adding heat and inturn it will dry up the towel making a higher RH.
Good luck with your grow. Id also think of throwing a few quick 56 day autos if you're planning on long vegging. You'll have more than enough space unless you doing a Scrog.