Growing Edge Technologies has built their Let's Grow A & B and Let's Bloom A & B, with certain manufactures fertilizer salts. G.E.T. owners have been building hydroponic plant foods for over 25 years and have tried the same formulas with different manufactures fertilizer salts, achieving different results and now we only build our plant foods with these proven mineral salts. 
 
SO LET'S GET STARTED Many manufacturers of plant food build their plant food to be pH stable. pH buffers such as 2-(N_morpholino) ethanesulfonic acid - abbreviated to MES will stabilize the nutrient solution. We, at Growing Edge Technologies (G.E.T.) build our plant food without pH stabilization capabilities, allowing the grower to monitor the nutrient solution and fix a situation before it becomes a problem with their yield. By monitoring the pH of the hydroponic nutrient solution, the grower can monitor the health of a plant. If the pH of the nutrient solution continuously rises then the plant is healthy and actively feeding. Do not allow the nutrient solution to climb above pH 6.5. Change nutrient solution, even if it is before the regular nutrient schedule change. There are two main reasons why the nutrient solution can drop in ph value. One is by not providing adequate volume of nutrient solution. If the volume of water containing mineral elements is not enough then the alkaline ions, such as, Ammonium Nitrate (NH4+), Potassium (K+), Calcium (Ca2+), Magnesium (Mg2+) will be utilized by the plant or plants quicker. Use a Parts Per Million (PPM) Electrical Conductor Meter to monitor the strength of nutrient solution. When the nutrient solution drops by 200-ppm you have to change the nutrient solution. Use 2 litre of nutrient solution per 4 days on small or young plants and up to 10 litres for large tomato plants. The second reason is that the plant is fighting off an invasion of bad bacteria in the root zone.