Virtualhost subsomains don't work with Dokku

I am using an Ubuntu 14.04 machine with Dokku installed. I followed the instructions in these tutorials

https://www.digitalocean.com/community/tutorials/how-to-use-the-dokku-one-click-digitalocean-image-to-run-a-ruby-on-rails-app

https://www.digitalocean.com/community/tutorials/how-to-set-up-and-test-dns-subdomains-with-digitalocean-s-dns-panel

And made sure to setup subdomains and everything else. The issue is I deployed a Rails app to a fresh Droplet and it was launched at the root of my hostname, rather than at the subdomain, as I thought it would.

In addition, when I go to this address:

sample.domain.com

It says the host name could not be resolved.

So I created a second app and deployed that too. Same thing at the subdomain of app 2.

Then I checked the docker processes, and I see this:

dokku/sample2:latest 0.0.0.0:49155->5000/tcp dokku/sample:latest 0.0.0.0:49153->5000/tcp

Both apps are mapping to the same port. Ok, I guess that’s ok as long as the virtualhosts work. But they don’t. So I don’t know what else to do.