Unable to figure out nginx config file of 2nd subdomain on ubuntu 16.X server

Question

I'm new to nginx server.

I need to run 3 different code bases based on domains and sub domains in ubuntu 16.X server.

domain.com
sub1.domain.com 
sub2.domain.com 

In my /etc/nginx/sites-available folder, I have created 3 files

domain.conf
domain1.conf
domain2.conf 

Here is the code in each file

domain.conf

server {
    listen 80 default_server;
    listen [::]:80 default_server ipv6only=on;

    server_name domain.com;
    root /var/www/html;

    index index.html;
    location / {
  if (!-e $request_filename){
rewrite ^/([^\.]+)$ /$1.html break;
 }
}

listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/domain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/domain.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

} 

domain1.conf

server {
    listen 80;
    listen [::]:80;

    server_name sub1.domain.com;
    root /var/www/app/angular_app/dist;

    index index.html;
    location / {
            try_files $uri $uri/ /index.html;
    }
}

domain2.conf

 server {
    listen 80;
    listen [::]:80;

    server_name sub2.domain.com;
    root /var/www/supportapp;

    index index.html;
    location / {
            try_files $uri $uri/ /index.html;
    }
}

domain.com and sub1.domain.com are working perfectly with http and https.

But when I type in http://sub2.domain.com, it is taking me to domain.com index.html file and when I type in https://sub2.domain.com, it is taking me to sub1.domain.com index.html file

nginx -t doesn't show any errors.

What could be the problem? How do I solve it?