I'm trying to figure out how to mix my top-off Rez for week 2. System is 100 Gallons. I plan to only mix my next week nutes in 20 gallons in the top-off reservoir (i'm guessing that's the max they'd drink at week 2). So am I calculating the nute schedule based on 100+20=120 gallons? So for instance, they recommend 1ml/gal of Veg A and Veg B so I put 120ml of A and 120ml of B in my 20 gallon top-off rez?