Network architecture behind reverse proxy

Hi!
I am running a container setup for a reerse proxy configuration where one container is the nginx reverse proxy and another one is the letsencrypt container (following https://linuxhandbook.com/nginx-reverse-proxy-docker).

Behind the reverse proxy I want to host multiple LAMP stack based web applications.

Question is whether all LAMP stacks should / need to be in the same network as the two containers managing the incoming traffic?
From different advisories I learned that the different LAMP stacks should all run in their own network due to service separation and security. But how will the traffic from the proxy then be routed to the LAMP containers?

Thanks in advance for any hint on that.

Best regards,
Olaf