I think I may have done something bad

Thank You everyone. I returned the clownfish back to my LFS and got in-store credit.

 

The damsels have established territories with the original percula in the tank. Then when you introduce a new fish into the tank they beat him up to maintain their territories. Dansels are VERY territorial. And as stated above, that is a small tank for that many fish, muchless damsels.
Just my .02

 

I can only agree with Steve.... Damsels are VERY territorial and agressive and I found that when I started my first tank my lfs recommended the damsels.... would NEVER do it again, I had to remove them because the kept bothering my other fish. So, either take them out or follow Steve's instructions. IMO it's better to take them back to your lfs.
Good luck and hope the clown survives!!

 

Is there enough current in your tank? Fishes will come up to the surface for more oxygen if they're having a hard time breathing. I'm thinking it lost some "slime" coating from being stressed and became vulnerable to parasites and whatnot. I suggest trying to get it to eat stuff soaked in garlic and those nutrient-enhancers (they come in a liquid bottle that can be bought at your LFS). I think that's your best bet along with increasing the movement of surface water. Do some more research too! Good Luck!

 

im suprised they dont kill each other aswell take them out and throw them out the window