A few soft stools were common with teething in my kids. A few loose stools is not diarrhea, diarrhea to your pediatricain will be frequency and looseness, causing dehydration, so a trip to the doctor will likely not be helpful at this point unless he starts having many movements an hour.
The acidity can be high in a teething baby, because of all the drool, I suspect. As long as he is acting normaly, and seems happy, just watch out for diaper rash, which we got very easily with the high acid. We had good luck using a hair dryer to keep the rashes at bay, and to dry them up if they got them. Use the dryer after every change, on low or no heat, and get him totally dry before diapering.
The eye teeth are the worst!
M.