2-install health check plugin.
deactivate theme and plugins using health check plugin’s troubleshooting mode
https://www.ads-software.com/plugins/health-check/

3-reactivate plugins one by one to see if it helps to narrow the source of the problem.
4-try an alternative theme like twenty sixteen if see if the issue continues

if you have a duplication of a plugin — figure out the proper one and delete the other. contact plugin support team to confirm latest version.