TV Wall mount permanent bracket arcs forward

Last night I installed the TV mount bracket on the drywall with two stud support. This was my first ever D.I.Y. lol. Meanwhile, it looks all fine and everything is in place but I noticed that the permanent bracket on which upper hooks are placed is arced forward like a bow and not clinging tightly on to the wall like I hoped (Picture attached). There is a gap between middle of the bracket and the wall. Can this be because of TV weight? My LED is 42′ inches and bracket is rated for 37-70′ TVs. Is this normal to have some elasticity in the brackets?
or do I need to add more support in the middle?