You can buy a ready-for-use/concentrated herbicide from HD or Lowe's that kills broad-leaf weeds (about $8/bottle). What you need is to hook up a tap water hose and spray on the lawn. Don't spray it onto tree leaves! It may be a bit late now, but you can still try. For future use: apply once in late fall and once in early spring next year; 99% of broad-leaf weeds should go.