You need more contrast on their faces, can hardly see their features. Like nose, mouth, eyes, the colors need to be way darker and more defined. Also in the ref pic, the guy's arms start from his hair and you can't see his neck, on yours it has a neck and shoulders and is diff stance. Idk it depends on how closely you follow the ref, I guess, but it puts a cool perspective to have him leaning forward bigger than the other dudes.