I've stopped giving them Gro all together so should not be the case. I use half tsp calimagic in 0ppm ro water, brings it around the 200ppm range. Then 1 tsp per gal of micro, 1 1/2 tsp per gal of bloom. 1 tsp per gal liquid koolbloom then 2ml per gal hydroguard. I am not using gro no more so...