Also, it is best to rinse your hydroton prior to your grow. I pour mine into a strainer basket and run water through it until the water shows absolutely no kind of redness in color, then I rinse the hydroton with boiling water for around 1 minute to sanitize it, then run cool water over again to cool off the hydroton and then it's ready to go into netpots. By doing this process, the hydroton's ability to interfere with your PH should be very minimal. I also would advise against using distilled. It will have higher variables in PH because the water has been purified of any and all PPM's, giving it a lesser ability to hold any ph value and more likely to shift. Tap will work fine, by rule of thumb, if it is under 250-300ppms, but ideally you want RO water. Tap should work fine though. In the case that you use RO water or any form of purified water, the application of a Calmag product MAY be neccessary, but not always.
For you Dahlioo, I would say to focus on these aspects of your grow to help solve your problem:
1. Get an airpump made for hydroponics, and match the output of air with the correct size and number of air stones. Unless you're using a giant 110lpm commercial pump like mine, 1 single medium or large size cylindrical ceramic air stone should be perfectly adequate. Too many airstones will reduce the bubbles in your water, not increase.
2. Make sure your water temps are being maintained below 70F and above 60F.
3. Try to get your hands on some Hydroguard, or another quality beneficial microbe product, OR, get your hands on some HORTICULTURAL grade h202. Regular food grade 3% peroxide may not be potent enough to sterilize your res properly, you need the plant grade 30%~ grade h202. Do NOT use h202 and beneficial microbes at the same time.
I forgot to mention this to the OP,
@Mistp65 , but food grade 3% h202 is not potent enough to serve as an effective sterilizing agent when mixed with your res water. It is already diluted heavily, then you combine that with many gallons of water and it simply isn't capable.