Aww... sorry to hear, its very sad news.
Don't feel bad, you did all you could. In all the years I have never cured a clown of Brooklynella. It's a nasty nasty parasite that really gets a clown fish when its already down. Make sure to leave your tank fowl without clown fish for month & a half.
Bet ya I can guess what pet store in Calgary you bought from. PM me the store, so its not to bash store to others here. Every time I have gone in their, I warn people, "see that's an example of Brooklynella. Don't buy anything in those tanks.
Regardless, sorry again for your loss. *HUGS*