Hi Joani:
I don't suspect your well water is the issue, rather, I suspect the harsh droughty summers of 2012 and 2013 as the main culprit.
The are other issues to consider as well: the physical quality of the tree when you transplanted it; care in planting the tree; planting the tree to deep or too shallow; over-watering and/or under watering; etc.
There is absolutely no way for me to determine the exact cause of "slow growth" via email, phone, or the Internet -- your best bet is to continue to evaluate the tree throughout the growing season next year.