Thanks a lot stinkyattic. I was thinking that myself because these girls are drinking quite a bit, almost 5 gallons a week in between reservoir changes. The combined reservoirs only hold 5 gallons. This week I am using liquid karma and RO only for top ups (following Latewood's schedule)and I noticed that the PPM fell from 1500 to under 900 in the 4 days since the reservoir change.

I was worried because I need to flip the lights to 12/12 in a couple days. The tallest plant is now 24" and all 3 are showing me that they are girls.