Just letting you know your post has been seen by someone who has not used that type of icing :( since you are new on this site U will not be able to reply to any post for about a month so if you have anything to say just start a new post referring to the one you talking about.
Someone will be along to help you soon I hope
It would be helpful if you would share the recipe. What are you using to sweeten the frosting? Without seeing the recipe, I suspect the tanginess comes from your artificial sweetener...........if you are using artifical sweetener, that is.