Hey, nice little grow you got going. I see you're having issues with your PH rising. I used to have a few problems with this as well but have developed a few techniques to control it-
-Pre-wash hydroton and soak in PH'd water for an hour prior to using
-Get a larger reservoir - Small amounts of water rise/fall much faster than lager amounts.
-Try using Silica Blast from Botanicare. PH to 6 and it will stabilize somewhere around 5.5-5.8 within an hour.
-Keep your reservoir clean, but don't change the water too often. Fresh water goes through a lot of fluctuations within the first few days unless you're using Reverse Osmosis. Stabilize the PH and top off the water as much as you can until it's time to change the nutrient solution. When topping off, a little humic acid derivative can help keep the pH stable.
Also, are you running a clean or living reservoir? Basically, are you using h202/DM Zone/etc or are you using beneficial bacteria? Aerated water at good temperatures (71 degrees or below) will increase in aerobic bacteria, and pH goes up. Even though the pH needs to be adjusted, aerobic bacteria are good for plants. If water temperatures get too warm, anaerobic bacteria will cause pH to drop. Anaerobic bacteria are the microbes that cause root rot. It is important that you take measures to control this in correlation to your pH levels.
Your nutrient solution should be fairly cool to temperate, somewhere in the range of sixty six to seventy one degrees Fahrenheit. You should be particularly aware of this if you happen to live in an unusually warm or cold part of the world. If you feel it is necessary to prevent plant deficiency, take extra steps insulate your grow room against outside elements. You should also try placing your reservoir directly on the floor, as the floor can be very cool, which can keep the reservoir cool in a warm grow room.
The most common deficiencies can be cured by adding a Calcium Magnesium supplement and an organic micronutrient supplement such as seaweed extract.
There are several additional products that can increase the availability of nutrients for your plants. Beneficial Bacteria are extremely important to keep roots healthy and clean. Beneficial Fungus will increase root growth. Enzymes clear out any dead root cells. All three of those biological additives can assist in breaking down nutrients for easier uptake by the roots and ensure a large, healthy root zone. Large roots have an easier time absorbing nutrients.
Humic Acid, Fulvic Acid, and B Vitamins can all increase plant metabolism and/or nutrient uptake.