Hi for a e few weeks apps on my nexus 7 keep crashing, skype crashes randomly, Google play crashed when I opened it ( I cleared the cache now when u go to download something it shows a grey screen) and other apps like doodle god crash randomly, also I when I turn my nexus 7 on I click the button to bring the apps up and it shows a swirl for a few seconds, I have around 3gb free what is wrong with my nexus 7?