Plants need co2 brought in low in the room. You can add co2 to the room or bring in a small amount of fresh air. You usually get enough co2 produced by just having a fan going.
Not sure if u got my pm, phone acting weird hope this chart helps for canna products
http://www.hydrogrown.com.cy/downloads/CANNA/feed_charts/terra.pdf
For veg my humidity stays between 30-50%. It really depends on where u r located tho. Your temps are pretty low so I would mess with the exaust and intake until you find the right sound your looking for.