Is it normal to drop 400 MMR in 2 games?

So 7 season starts, and I decided to start my placements. The first 6 games went really well, and my MMR was about Silver 5. But then I play my next game, and I lose about 75 MMR. It wasn't too much of a drop, and then I play the next game. I lose that one too, and I lose 300 MMR. Went from bronze 1 to Bronze 5 in a flash. How???? It was so difficult to earn 300 from the first 6 games, and I lost 400 in a matter of about 2 hours. Is this how MMR works? Now I'm placed in Bronze 5, and super discouraged on how just 2 games made me lose more MMR faster than I gained in my first 6 games. Can someone please explain?