How to add custom headers to some responses

Using Traefik version 1.7.12 on Service Fabric, I'd like to add a custom header to certain responses returned from a particular service. It seems the only way to do this is to re-deploy the service with different labels. The problem with this is then I'll end up with 2 backends. In my case, this means 2 set of docker containers.

Is there a way to map multiple frontends to the same backend?