I have a 128gb iPhone 6S Plus and today it just randomly filled up its storage to almost full. Last time I checked I was only using 35gb and I haven't downloaded anything huge since then. I'm thinking it might be a corrupt app but under the storage section in Settings none of my apps have jumped a huge number. --- Post Merged, Feb 23, 2016 --- Yep, I just added up what's shown in Settings. It's 33.4 gb used and it says I have 111.11 gb used.