When you first change and you have an over all PPM. Your plants drink nutes and mostly water, the ppm will go up and then you top off with water and your ppm's will come back to very close to what you started with. Only top off with water. Then PH to 5.8 or close. Don't add anything more. If there is a slight change it's the plants eating nutes and giving off waste, so you really don't know what they ate so adding back is a guess. You might add too much of something and screw up the mix.