Inconsistent pH from Pinpoint and Milwaukee

After cleaning my pH probe in vinegar, followed by multiple DI rinses, I calibrated my Neptune apex with pH standards from Pinpoint. I also ordered a pH 10 standard from Milwaukee so that I could have a second standard to compare too. After calibrating to the pinpoint standards, (6.98 reading in the 7.000 and a 10.01 reading in the 10.000) I decided to test the pH of the Milwaukee pH buffer. The pH read 9.80 with the Milwaukee 10.01 standard. I rinsed the probe and reinserted in my pinpoint standards and got the same readings as when calibrated. I then rinsed the probe and put it back into the Milwaukee and it is 9.8 again.


I found an article by randy that shows deviation of different pH standards, but none seem to be as high of a difference as I am seeing. http://ift.tt/2lxtx39

I am going to order a few set of calibration solutions from both pinpoint and Milwaukee and test it again. In the mean time I am not sure which value to trust. After the calibration the pH in my tank reads 7.8 night and 7.95 day, which seems a little low to me but I do have lower levels of alk (8 dkh). I have never been chasing a specific pH for my tank as that can lead to problem with excessive buffers, but i feel that 7.8-7.95 is slightly on the low side, and beginning to think about adding outside air to increase it.

What do you think about my pH and the calibration.