Can someone outside of the lan uses my nginx proxy?

I know this question can sounds weird but I noticed strange behaviour on our network.

Here's the context:

I have a vm running multiple docker containers. To simplify their use and because I need https we set up a nginx reverse proxy in a container jwilder/nginx-proxy (following this method https://www.singularaspect.com/use-nginx-proxy-and-letsencrypt-companion-to-host-multiple-websites/)

I am seeing some requests sent to multiple ips addresses during the night on an unknown port :

@myserverip  48772 =>     18.97.91.16 9001 
@myserverip  59094 =>  19.170.104.214 9001 
@myserverip  35308 =>  19.189.157.180 9001 
@myserverip  52786 =>   25.13.210.166 9001 

For the moment iptables allow everyone to request 80 and 443 and the reverse proxy container is the only container mapped on these port. I filtered all incoming connection and no more connection to these ips.

Can someone from the outside uses the reverse proxy ?