Boesemani Rainbow Scale Growing Cotton Like Wounds

My rainbow got this about three days now. I have tried water changes and Melafix but it seems to get worse.(the white cotton like wound gew bigger)
 
Here is the picture. Does anyone know what exactly this is? I have some in mind but the treatment i been giving is not working.
 

It looks like a fungal infection and Melafix is designed for general bacterial conditions so you might want to try and find something specifically for treating fungus. I believe salt water baths might help too.
 
Where in the world are you?  

Thank you Jetman. I just managed to find a old API fungus cure pack (not expired yet) =) I will give it try if the condition gets worse. Do you have any med suggestions?
 
As for the Melafix it does say body slime & mouth fungus.... 
 
I am located in seattle WA