Losing fish to vortechs :(

[dynamite]

Thanks again for all your replies... Well I have BAD news...
Just when things couldn't get WORSE... Not receiving anything of what I bought online for my tank or the present I bought my dad for Father's Day.. because of the Canada Post's strike (Thank you I'll start using UPS).
I just saw that my small Yellow Tang 2in.. Once healthy... has a few tiny black spots.. So I'm guessing it's black ich.
It's the 1st time in 3years with this tank that one of my fish gets sick and the worst part it's I don't know what to do!!! He seems healthy he's swiming, playing and schooling with the other fish like always and he's pooping huge green poop He seems ok.. But I don't know what to do! I don't want him to die or my other fish to get infected! What should I do??? I don't have a quarantine tank It's the black ich going to go away if I keep him "healthy" and well fed? And what caused this black ich outbreak?

SOS!!!