Originally Posted by LBA4ME
No. The buffers I used to calibrate were old and in fact the last little bits left in the bottles.
That cast's suspicion on all your observations. When you take a pH measurement you are comparing the sample to the buffer. If the buffers are off, your measurements are all off too.
As I noted earlier it doesn't seem likely that you would have such low pH given the the water and grain bill - even with the roast barley ground up fine. Possible, but not likely.