small problem

ok so my reservoirs hav been doin somethin weird lately. the water gets real foggy and the ph goes up. if i let it go 24hrs it will go up 1.0. i'm a seasoned grower and i've never seen anything like it. the plants still look good but hav slowed considerably and the only factor that has been affected is this water issue. i've asked my local gro shop as well as a few friends that also gro and they all say the same thing. the only thing they r on is Humboldt County's Own Gravity. i use a little of Potash+ in one and they both get Zone root stabilizer. i took away the zone and it didnt change anything.
any help is appreciated