Q: Apps won't open

For a week my Tumblr app would not open. It finally started working 2 days ago. Then this morning I realized about 85% of my downloaded apps will not open. I click on them, they open a blank page, then immediately close. I think it might have something to do with my 9.2.1 iOS update. How can I fix this issue? I have tried deleting the apps and downloading them again and that doesn't work. I have also tried turning my phone off and that doesn't work. Help!