Could it be her tear duct again?

My daughter was born 6/3/06 and her doctor had said that one of her tear ducts were blocked or underdeveloped and it will improve in time which it did. For the past two months she has been tearing often out of her left eye. Do blocked tear ducts sometimes come back or is it maybe something else? I'm in the process of making her an appointment to see a doctor, but I'm curious to what it is and how it will be treated.