EC (the measure of nutrient levels) and pH (the acidity of your water) are both a vastly integral part of the hydroponics process. When adding your own mix of nutrients, it is important to make sure you are not over or under feeding and that the mix you are giving your plants can be readily taken up. If your nutrient ratio is wrong, you could risk shocking your plants, leading to reduced yields just as if your water is too acidic or alkaline, you could bring on leaf deficiencies and even permanently damage your plants. Make sure you keep on top of your pH and EC for best results.