Normal
The sourness I noticed a week ago is related to a similar habit I have when I smoke while working. Too much exposure to the same section of mouth tissue can lead to irritation, white or red discolouration, inflamed pappillae, loss of taste or uncharacteristic oral responses like sourness and bitterness and metallic tastes. I'm sure most of us have experienced some of these symptoms at one point or another pursuing our hobby. I cut back my bowls per diem and the issue is subsiding. Too much of a good thing...