Base Rail Bent

I just noticed the front base rail, the rails in the bed of the truck the hitch attaches too, is bent. It is the rail closest to the cab. There are three bolts securing it to the truck. It is bent on the driver's side of the center bolt.
So what did I do to bend it? I tow a 8k 30 ft 5er. Hitch rated to 16k.
Plan on replacing rail myself so is there anything I need to watch for?