I've never used GH. Are you checking PPMs? If so my guess is that they are dropping hard. If so try raising your solution to 1050-1100ppm? The only time my res seems to drop in pH is weeks 3-5 of flower, when they are really eating a lot of potassium. Feeding them higher may help. Also...
The Vivosun Bud Factory
Kush Mints Clones in RDWC
Featuring the VIVOSUN Smart Grow System and the VSFD6500
Sponsored by VIVOSUN
Welcome back to the Vivosun Bud Factory, a Vivosun 5x5 (60x60x80) advanced grey tent equipped with a custom Vivosun Smart Grow System (SGS) with a Vivosun VSFD6500 and...