pH issues

[Dmev60]

So I have had my tank (RedSea Max 550) for over 3 years and it has been doing great overall. I have many fish from when I first set up the tank, and I have many corals that have seen excellent growth. I got a Seneye a year ago (2018) at Christmas and have been monitoring my tank with it with great results. I also check my other parameters weekly with various RedSea test kits and typically get good results. Awhile back I started having issues with elevated pH. Some of my corals started to fade and I lost a couple of my newer fish additions. I did a 50% water change 2 weeks ago hoping this would help with the issue but the elevated (8.5 to 8.6) pH returned right away. I looked at some of the additives I was dosing with but none indicated any conflicts with pH. I did some research online and starting dosing with some distilled white vinegar. The pH would respond and lower temporarily but then would rise back up over several hours later. I purchased a Hanna Checker plus Ph meter and after doing a 2 point calibration measured my tank water and found that the pH was actually about 7.54! Yikes! All this time I was dosing to lower my Ph, I was actually driving it down to an unacceptable level. I began dosing with baking soda to bring it back up and the Hanna Checker indicates that I am back up to around 8.00 now. And I changed the slide in the Seneye thinking that maybe I had a defective one. But my Seneye is reading a Ph of 8.38. My question after all this background info is can you and how do you calibrate the Seneye? I went on their website and they say no calibration is necessary as each slide is calibrated already. I am at a loss as to what to do and would appreciate any feedback/suggestions.

 

[Uncle99]

Any PH in the 7.8 to 8.3 range is fine, don’t waste time chasing this parameter.
When tests show either real low or high PH readings I tend not to trust that test.
My tank has run between 7.9 and 8.0 for 30 years.