When Summer asks the teacher to look up the file on Brown, she looks at her computer screen. The only program running is iTunes, so she could not have possibly checked up on the file.
During Marissa's flashback to Trey's shooting, there is a shot of the blood starting to drip from his exit wound in his chest. Not only was Marissa behind him the whole time of the shooting, he was also bent over Ryan. There is no way Marissa would have seen the wound from that angle.
While at the surf competition, it is a bright sunny day. However, when Johnny, Chili, and Marissa are talking, and later when Ryan, Johnny, and Marissa are talking there is no sun on any of their faces. It is obvious they are standing under something so the glare isn't on their faces.