A player losing his quality? How did it happen?

[sincity]

I saw on a friend's team that several of his players have lost quality? They were Q 136 or 137 and they are now Q of 135. And actually all of his team is Q 135 now, some players increased their Q to 135, but some decreased so that they are all equal at 135 Q now. How on Earth did that happen? I am on my 26th season now and had not seen a player's quality decreasing. Has there been a change to the game or a new update which makes it possible to equalize the quality of your squad players or perhaps it's just a glitch?