So if nature magic can do something then why can't the red flight use nature magic to do that as well? The green flight wasn't about healing but about nature. They received their gifts from Eonar the same as the red flight.
What about the red dragon that healed the corruption of a black dragon egg? You know the story of how Wrathion was born. https://wowpedia.fandom.com/wiki/Rheastrasza
What about a Red Dragon healing other red dragons? https://wowpedia.fandom.com/wiki/Draconic_Mending and https://wowpedia.fandom.com/wiki/Vermillion_Mender