I have a 6w from clone plant, just switched to 12/12 today. This past week, the reservoir seems to be down about 1gal/day. Sometimes a bit less (0.7), sometimes a bit more (1.1).
Humidity in the grow room is about 54% 24/7. I have a 8" inline fan exhausting the 100sqft room, and three fans blowing in the room.
Using RDWC (a first grow with one plant, future grows will have more).
Is that to be expected? If I run 6 plants, it should be around 6g/day, right?