I don't think your friend will like you very much if you were to introduce Ich into his tank. I don't know what to tell you really. This is a good lesson to you and your wife though.Tangs never do well when overcrowded. The foxface would be fine by itself in your tank but when you add a yellow and blue to that small of a tank this is the kinda thing that happens. Aggresion is not always visble.i.e. chasing or torn fins. Non physical aggresion can be just as bad.I am so sorry I know you love your fish and it sucks.