Sudden CPU 100% with php-fpm on Wordpress website

Hi everybody,

so two days ago something happened (no updates, no changes of configuration) and my droplet started non responding. Ever since the CPU is at 100% (unless I systemctl stop httpd) and more specifically the php-fpm process. More specifically is one user, for which the error.log il filled up with strings of this sort:

[fcgid:warn] [pid 20704] [client xxx.xxx.xxx.xxx:xxxxx] mod_fcgid: can't apply process slot for /home/xxx/fcgi-bin/php7.1.fcgi, referer: https://www.youtube.com/results?search_query=jKOJ5Bs

(Sometimes is google, bing, yahoo, …). So I though it was a DDOS attack and I thus made a new rule on my fail2ban like so:

[http-get-dos]
enabled = true
port = http,https
filter = http-get-dos
logpath   = /var/log/varnish/varnishncsa.log
maxretry = 100
findtime = 30
backend = polling
journalmatch = 
banaction = iptables-multiport
action = %(action_)s

(I specify polling because on default varnish runs on systemd). The configuration seems to work, and in fact if I run fail2ban-client status http-get-dos I do get some bans (currently 6).

However the CPU is still 100%… Any other ideas? Something else to look at I may be missing?

Thanks