If you have published the App and it had 4 base sheets, and when User1 duplicates it and creates 4+2(his sheets in personal space) and User2 duplicates it and creates 4+3(his sheets in personal space). If you want 4 base sheets + (User1 - 2 sheets and User2 - 3 sheets ) totally 9 sheets into an app then there is a way to do this.
Consider you are a Adminuser, Go to the App objects in the QMC and find all the 9 personilaized sheets done by User1 and User2 and change the owner name it your name. So now all the Sheets will show in app when you launch the app in Hub under my sheets for Admin user.
Now you have all sheets consolidated at one place you can publish all the sheets under adminuser.