SPRINGFIELD — The grandparents of a slain 2½-year-old child have renewed a push for judges to impose tougher sentences on defendants convicted of killing a minor.Greg Williams, and his wife, Marsha, lost their granddaughter, Reagan, on July 2, 2006. Reagan was a victim of child abuse at the hands of her mother’s then-boyfriend, Ryan Allhands.Allhands, who was charged with first-degree murder in Reagan’s death, pleaded guilty to involuntary manslaughter in December 2009 and was sentenced to seven …