What happened to 49ers' running game?

Daily 49ers blog for NBC Bay Area website: Earlier this season, the 49ers were grinding out big yardage each game on the ground. The past three games, that hasn't happened. What's the reason? https://www.nbcbayarea.com/news/local/Niners-Need-to-Get-Back-on-Track-With-Running-Attack-565280401.html