TTFB for mobile is over 3000ms!

[mreinders]

When testing my site for desktop browsers I get great grades for my site (click here), but when I test the same page against mobile versions my TTFB is over 3000ms (click here).
What could be causing this?
Could I have done anything in the wordpress dashboard that caused this? Or is this as back-edn/server/sql/php problem that the person with FTP access to the CPanel needs to address?

Any information is helpful.
Thanks,
Mreinders