Dropbox and the ever expanding Itunes lib

[BigJohno]

So I have been using Dropbox for 6 months to store my itunes library. I have an imac at home and I also use an MBA. I use dropbox to keep the music in one place that way both computers are synced up. My problem is that for some reason my itunes library is slowly expanding and now I have no room on my dropbox. I have 26Gb of music and no podcast and another folder with about 4gb in it and it tells me that I have used 99% of my 50gbs. What gives. What could be causing this?

 

[BigJohno]

So looking around in my itunes folder I found the mobile application folder and says there is 9gbs in it. Now I went through and deleted my apps that I dont use and I only have about a gig maybe of apps.