Thanks for the reply guys, yes it's a recirculating system with 75 gal res. Ph has been very stable at 6.0, I usually bring it to 5.8 and adjust at 6.0. I dumped res and added armour si 1mil/gal, 2mil/gal micro and grow, 1 mil/gal bloom and 2 mil/gal calimagic, no other boosters. PPM are at 440...