Here are items to check:
1. Produce a browser trace to show the time it takes to load page(s).
2. Review the Administration > Security and Diagnostics > Log Analysis page.
In order for the graphs to be populated, make sure the job (Tomcat access log import/analyze) is ran on a daily basis.
3. Make sure the database requirements from the documentation have not changed or there have not been any network/server changes.
4. Is there high memory or I/O usage on the application server?
5. If requested, obtain and attach the following to the case in a ZIP/RAR file:
For Oracle, provide the html version of the AWR report.
For SQL Server, provide the Top Performance reports.
For PostgreSQL, provide the Badger report.