My current Personal Rank Adjustment seems extreme

Hi, I have not played Heroes for a month now, until yesterday. When logging on I was in Platinum 1, and after 4 games my rank adjustment has been -12, -16, -18 and -19. I currently have 68 wins and 69 losses this season, and all of them seemed to be fairly balanced; no crazy streaks.

What’s the deal? Why am I losing almost 20 points per game to rank adjustment despite an almost exact 50% win rate?