workflow2013 – Sharepoint workflow 2013 working very slow

I have problems with my sharepoint. It's 1 month my workflow 2013 working very, very slow, 2010 working fin. I have tried several solutions but my problem was not solved. We have 2 applications, 2 web servers, 2 DB and 2 wcf.
I have tried
1. Install updates,
2. Delete all workflows for 2013 and start only a workflow that records the history,
3. Change the workflow performance (accelerator size, batch size, and so on),
4. Rebuild the Workflow Service Application Proxy,
5. Change the Proxy server from the application workflow application server to the web server,
6. Stop all harepoint workflows
7. Turn off the custom servers (in that situation when the problem is with one of my servers)
The problem started unexpectedly. We have not changed anything. Moramia is fine, the CPU is fine, the jobs work well.
Is there any idea?
Please heeeeeeelp !!!