Vertical PVC Hydroponic system ... hydrogen peroxide

So im currently in the middle stage of heavy flowering. 12 12 cycle. I built and use a vertical PVC pipe Recurulating system, and am growing Big Bud, and Afgan Kush. I am using 2 105 watt 2700 kelvin, one 150 Hps and smaller CFLS around. My question is that my system has been maintaining a constant PH of about 5.7 and i increased from 500 ppm to late veg 1500 ppm and eairly flowering, current levels i try to keep at 5.8 and 700-800 ppm. I have routine soutution changes and keep the same gardening schedual every day. I use foxfarm nutes and ph down to adjust. I just researched the use of hydrogen peroxide 3 percent, in the system and was wondering if anyone had any other helpful information on the use of hydrogen peroxide. Also if anyone has experienced or has any knowledge of why my system was so stable with the PH, and in middle to late flowering why it is constantly lowering and i need to adjust constantly the past couple of days

u use hydrogen peroxide when ur water is too warm....69+
u want hydrogen peroxide 30 percent not 3. hard to find in the pacific northwest