Wordpress site crashing whole server without error message

A wordpress site was working properly, suddenly, it stopped working, properly something was done unintentionally.

Wordpress version is 4.4.2 running on Ubuntu 14.04

The site does not load, and then all the other sites on the server stop loading!

I got an error in apache error.log

[mpm_prefork:error] [pid 1047] AH00161: server reached MaxRequestWorkers setting, consider raising the MaxRequestWorkers setting

It seems that the theme or one of the plugins is causing issues We hav

It seems that one of the plugins is causing

via Chebli Mohamed