By Daphne Psaledakis and Kanishka Singh WASHINGTON (Reuters) – The European Union and the United States urged Serbia to address concerns about its electoral process after independent observers found worrying irregularities including vote buying during Sunday’s snap election. The electoral process in Serbia, which has been a candidate to join the EU since 2012, needs to be improved significantly, two EU commissioners said on Tuesday. “We conclude with concern that the electoral process requires tangible improvement and further reform, as the proper functioning of Serbia’s democratic institution…