First month of 11v11 and our midfield three are miles apart

I’d coach the distances before I coach the positions. In a midfield three, the 6 and two 8s do not need fixed zones, but they do need to keep giving each other useful passing angles. The problem in your picture is not that one 8 has gone wide or the 6 has dropped. It is that nobody has reacted to those movements. I’d give them two references. First, if one midfielder moves away from the centre, who reconnects underneath or inside? Second, can the player on the ball see two midfield options rather than three players on the same line? A 6v6+3 or 7v7 directional game is useful because the midfielders repeatedly have to adjust around the ball without standing on markers. I’d also let the three review clips together. At U14 they can start recognising when their own movement has stretched the unit. The aim is a midfield that can change shape without losing connection.