The new library doesn't need any of the previously approved assets. Try not using the 'add all changed resources' button, I've found that it confuses most people and gets in the way of a more linear workflow.
There might be a specific workflow that will work for you... Try this idea and let me know if it makes logical sense as something reproducible... I've found this workflow the best way to get people started on Launch's complex library mgmt and build-to-environment workflow.
5 Step Process to Making Changes with Adobe Launch
1. Go into publishing, Make a new library
---Do NOT add anything to this library---
---Do NOT hit the 'add all changed resources' button , in fact , NEVER use that button!!!!---
2. In the top-right corner, you should see an option for "Working Library" , select your new library.
---Now you can start the work that you'd normally do---
3. Whenever you add or update a rule, data element, extension, etc... Just remember to bit the "Save to Library and Build" option.
---Quick tip if you work with a single dev library in the property: If you already made the changes to the asset but it's not in your library: just open the item again and then hit "Save to Library and Build".---
4. After you've done your quick changes, you can now go back to the publishing tab.
5. Approve the new library through the publishing workflow as usual
(remember, you don't need to add anything to your library, you already did that automatically with "Save to Library and Build").
6. Repeat step 1...