A little help

[Canadbis]

So over the last week I have been siphoning out little red bugs. Flat worms are what I found them to be, and on sunday I did a dose of Flat worm exit. Man that stuff works as good as an H-bomb, As they were dieing I siphoned out the dead bodies and the cobweb looking things that they left behind. I watched carefully and after about 3 hours I noticed non of my coral were opening up so I proceeded to do a 30% water change and again watch. Monday I took the afternoon of to do a little more maint as I wanted the rest of these darn things out. When I went to bed last night everything was going fine. All fish were eating, the crabs and shrimp were doing their thing, corals and such looked good, but this morning I woke up to my Yellow tang dead.
Do you think it was from the flat worms? I am at work now so there is no way I can get home to do a water change or even checkon them.
I need some Ideas, anything that you think would help fix things or understand what I did wrong, or need to still do.

[fencer]

Did you run carbon?

[MikeP]

Maybe the stress of everthing just caught up with him? How do the rest of the fish look?

[Canadbis]

Yes and I still am running carbon, it will be removed tonight.

Everyone else looks fine, as of this morning, haven't checked them since.
When I went to bed last night everything/one was fine

[Canadbis]

Everyone looked good lastnight and this morning. Stress from something I guess, if it was poisoned I would think other things would have died with it.

[Der_Iron_Chef]

Some fish are definitely more resilient than others, and I've found the yellow tangs to be less resilient than most. Just my own personal experience.