Curl do Docker Container on same Docker Host (nginx-proxy) - wordpress

Question

I have a setup based on docker-letsencrypt-nginx-proxy-companion running a django container and a wordpress container on the same Docker Host. I have added to domains to each of the container, so the wordpress container is reachable with mydomain.com and www.mydomain.com and the django container with subdomain.mydomain.com. This is configured in the VIRTUAL_HOST env and its working perfectly so far. I get all certificates and I can connect to each of them.
The main Issue I have now is, that the wordpress container needs to curl the django container and vice versa. But if I go into the django or wordpress container and try to make a call to e.g. subdomain.mydomain.com I get the following error:
$ curl mydomain.com
Hostname was NOT found in DNS cache
and then he tries to connect to the IP and is ending up in a timeout. If I make a curl from local or a different server I get a 200 without any problems on each of those. I read sth about a DNS resolve issue but atm I couldn't find a solution. Do you have a clue what I could do in this case?
Thanks in advance!
My Containers:
Nginx Proxy Compose
version: "2"
services:
nginx-proxy:
image: jwilder/nginx-proxy
container_name: nginx-proxy
restart: always
ports:
- "80:80"
- "443:443"
volumes:
- "/var/www/certificates:/etc/nginx/certs:ro"
- "/etc/nginx/vhost.d"
- "/usr/share/nginx/html"
- "/var/run/docker.sock:/tmp/docker.sock:ro"
letsencrypt-nginx-proxy-companion:
image: jrcs/letsencrypt-nginx-proxy-companion
container_name: letsencrypt-nginx-proxy-companion
restart: always
volumes_from:
- nginx-proxy
volumes:
- "/var/run/docker.sock:/var/run/docker.sock:ro"
- "/var/www/certificates:/etc/nginx/certs:rw"
networks:
default:
external:
name: proxy-network
Wordpress Compose
version: '2'
services:
mariadb:
build:
context: .
dockerfile: build/env/mysql/Dockerfile
env_file: .env
restart: "always"
ports:
- 3306:3306
environment:
MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
MYSQL_DATABASE: ${MYSQL_DATABASE}
MYSQL_USER: ${MYSQL_USER}
MYSQL_PASSWORD: ${MYSQL_PASSWORD}
volumes:
- prod-database:/var/lib/mysql
php:
build:
context: .
dockerfile: build/env/php-fpm/Dockerfile
env_file: .env
restart: "always"
volumes:
- ${SRC_APP_PERSISTENT}:/var/www/html
links:
- mariadb:mysql
web:
build:
context: .
dockerfile: build/env/nginx/Dockerfile
restart: "always"
links:
- php:fpm
volumes_from:
- php
environment:
- VIRTUAL_HOST=mydomain.com,www.mydomain.com
- VIRTUAL_PORT=443
- VIRTUAL_NETWORK=proxy-network
- LETSENCRYPT_HOST=mydomain.com,www.mydomain.com
- LETSENCRYPT_EMAIL=info#mydomain.com
ports:
- "80"
volumes:
prod-database:
driver: local
networks:
default:
external:
name: proxy-network
Django Compose
version: '2'
volumes:
postgres_data_dev: {}
postgres_backup_dev: {}
services:
postgres:
build: ./compose/postgres
volumes:
- postgres_data_dev:/var/lib/postgresql/data
- postgres_backup_dev:/backups
environment:
- POSTGRES_USER=dbuser
django:
build:
context: .
dockerfile: ./compose/django/Dockerfile-dev
env_file: .env
command: /start-dev.sh
depends_on:
- postgres
environment:
- POSTGRES_USER=dbuser
- USE_DOCKER=yes
- VIRTUAL_HOST=subdomain.mydomain.com
- VIRTUAL_PORT=443
- VIRTUAL_NETWORK=proxy-network
- LETSENCRYPT_HOST=subdomain.mydomain.com
- LETSENCRYPT_EMAIL=info#mydomain.com
volumes:
- .:/app
ports:
- "8000"
links:
- postgres
- mailhog
pycharm:
build:
context: .
dockerfile: ./compose/django/Dockerfile-dev
depends_on:
- postgres
environment:
- POSTGRES_USER=dbuser
volumes:
- .:/app
links:
- postgres
mailhog:
image: mailhog/mailhog
ports:
- "8025:8025"
networks:
default:
external:
name: proxy-network