first time with hydro, I have a six bucket system with a reservoir and controller...using r/o water and good nutes...system has been up for 3 days...evry day the ph drops.....a lot at first, from 6.2 to 4.5 over night...today from 6 to 5.5...using hygromite medium..is this normal at start up? will I have to balance every day? temps are 70 degres.. 20 gallons in the reservoir....thx for any help..