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.