docker stack deploy is not working properly but docker-compose is working properly

Question

I am new to docker swarm and docker compose.

I built an application that uses a nginx and flask docker containers. nginx acts as a reverse proxy.

when I am building this entire application using docker compose everything works fine

my docker-compose.yml file

version: '2'

services:
  web:
    restart: always
    build: ./web
    image: shivanand3939/web
    expose:
      - "8000"
    volumes:
      - ./output:/usr/src/app/static
    command: /usr/local/bin/gunicorn -w 2 -b :8000 --access-logfile - classifierv2RestEndPoint_ridge_NB:create_app()

  nginx:
    build: ./nginx/
    image: shivanand3939/nginx
    ports:
      - "80:80"
    volumes:
      - /www/static
    volumes_from:
      - web
    links:
      - web:web

  viz:
    image: dockersamples/visualizer
    ports:
      - 8080:8080/tcp
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    environment:
      - "constraint=node.role==manager"

Below is my output:

however, now I want to take it to the next level by deploying it in 3 AWS instances

here is my docker-stack.yml file

version: '3'

networks:
  mybridge:

services:
  web:
    restart: always
    build: ./web
    image: shivanand3939/web
    expose:
      - "8000"
    volumes:
      - ./output:/usr/src/app/static
    command: /usr/local/bin/gunicorn -w 2 -b :8000 --access-logfile - classifierv2RestEndPoint_ridge_NB:create_app()   
    networks:
      mybridge:
        aliases:
          - web
    deploy:
      replicas: 2
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  nginx:
    restart: always
    build: ./nginx/
    image: shivanand3939/nginx
    ports:
      - "80:80"
    volumes:
      - /www/static
    networks:
      - mybridge
    deploy:
      replicas: 1
      update_config:
        parallelism: 2
        delay: 10s
      restart_policy:
        condition: on-failure

  viz:
    image: dockersamples/visualizer
    ports:
      - 8080:8080/tcp
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    deploy:
      placement:
        constraints: [node.role == manager]

But now when I deploy this application and check the URL I am getting this

[incorrect home page]

I am not understanding why in the first case there was communication between web and nginx containers but in the second case this communication is stopped.

Can anyone please guide me on this

UPDATE 1:

Upon looking at the nginx service logs I see,

classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:50 [error] 5#5: *10 "/usr/share/nginx/html/phpmyadmin2013/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmyadmin2013/ HTTP/1.1", host: "35.154.66.136"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 10.255.0.2 - - [11/Sep/2017:06:49:50 +0000] "HEAD http://35.154.66.136:80/phpmyadmin2014/ HTTP/1.1" 404 0 "-" "Mozilla/5.0 Jorgee" "-"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:50 [error] 5#5: *10 "/usr/share/nginx/html/phpmyadmin2014/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmyadmin2014/ HTTP/1.1", host: "35.154.66.136"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 10.255.0.2 - - [11/Sep/2017:06:49:51 +0000] "HEAD http://35.154.66.136:80/phpmyadmin2016/ HTTP/1.1" 404 0 "-" "Mozilla/5.0 Jorgee" "-"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:51 [error] 5#5: *16 "/usr/share/nginx/html/phpmyadmin2016/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmyadmin2016/ HTTP/1.1", host: "35.154.66.136"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:52 [error] 5#5: *17 "/usr/share/nginx/html/phpmyadmin2017/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmyadmin2017/ HTTP/1.1", host: "35.154.66.136"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 10.255.0.2 - - [11/Sep/2017:06:49:52 +0000] "HEAD http://35.154.66.136:80/phpmyadmin2017/ HTTP/1.1" 404 0 "-" "Mozilla/5.0 Jorgee" "-"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 10.255.0.2 - - [11/Sep/2017:06:49:55 +0000] "HEAD http://35.154.66.136:80/phpmyadmin2018/ HTTP/1.1" 404 0 "-" "Mozilla/5.0 Jorgee" "-"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:55 [error] 5#5: *18 "/usr/share/nginx/html/phpmyadmin2018/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmyadmin2018/ HTTP/1.1", host: "35.154.66.136"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 10.255.0.2 - - [11/Sep/2017:06:49:57 +0000] "HEAD http://35.154.66.136:80/phpmanager/ HTTP/1.1" 404 0 "-" "Mozilla/5.0 Jorgee" "-"
classifierbot_nginx.1.qhi4b9c1yc3n@ip-172-31-16-132    | 2017/09/11 06:49:57 [error] 5#5: *19 "/usr/share/nginx/html/phpmanager/index.html" is not found (2: No such file or directory), client: 10.255.0.2, server: localhost, request: "HEAD http://35.154.66.136:80/phpmanager/ HTTP/1.1", host: "35.154.66.136"