I think with a grow room that size any attempts to alter the humidty levels is a waste of time and effort.

Remember if you have a small space and you have really good circulation, its the OUTSIDE AIR COMING IN that you would have to alter....not the air INSIDE.

No I do not think you have to worry about it. If you would like to tinker and try to achieve perfection, I would buy a $35.00 humidifier at Walgreens and put it near my closet air intakes.

But for that small space, you will be fine I think