Yellow Tang Help!

[Funky_Fish14]

Another thing to note(thanks Catherine and Kevin!) is that my clam is always opened very nicely and has yet to 'complain', per say, about the water params. Also, all the other corals appear just as happy as usual! The fish also see to swim fine and dont look stressed at all. I have simply lost them just like that. The last one to die, I did not see it act the way the others did, but I didnt see it do much at all. It was fine one evening when the lights went off, the next evening within 24hrs it was dead.

Thanks for any/all the help!

Chris