I'm using all mixed from the bio bizz range, in week 5 of flowering, my PH is around 6.2/6.5 when adding nutrients then applying it to the plants /top -max bio-bloom bio- grow. Appreciate the reply cheersIf you tell us more about your grow then we can perhaps point you towards corrective action.
Stuff like, medium, feed mix / ppm / pH, water source / ppm / pH.