When Boruto fires his Rasengan it varnishes. What type of Rasengan did Boruto use?
When Boruto is trying to convince Sasuke to train him, he creates a small rasengan infused with wind chakra.
Though Boruto's Rasengan is initially much smaller, he subconsciously applies wind-natured chakra to it, enabling him to hurl the Rasengan across distances. While it loses its physical form shortly after bring thrown, the wind and force continue on-course unseen, tricking the opponent to let their guard down as sufficient damage is inflicted when it makes contact. Boruto eventually becomes able to create a normal-sized Rasengan after more training. - naruto.wikia.com/