Mysterious Clown Sickness

[alix]

OK im new at this, only about 2 yrs experience. in my 20G i have 3 ocellaris clowns and 1 yellowtail damsel, along with a ton of snails, crabs, a conch, and a curly q annenome. so heres what happened. one morning i woke up and turned my tank light on, usually when i do the the 3 clowns are huddled together on the bottom... sleeping i think... but this time they were on different parts of the sand on their sides gasping. i checked all my parameters and everything was fine, i thought they might need oxygen, so i hooked tubes up to my powerheads to aerate the water, and put the fish in a breeder net, because if they tried to swim or floated to the surface, they got pushed areund or stuck to an intake. this was bout 3 weeks ago, they are still in the net, they seem better a little, but i think they might be brain damagd? they spin around alot, lay on their sides, and dont socialize like they used to. one seems to have strange marks on it. i was wondering if anyone has had this happen to them, (the damsel is unaffected, and i though it was strange that all the clowns got sick at once) maybe the annenome stung them at night? and what anyone thinks i should do. id really hate to kill them they dont seem like that are suffering, but if it has to be done ill do it.
TY IN ADVANCE FOR ANY SUGGESTIONS/HELP!!!!!!!!!
EDIT (i wanted to add that this tank has been running for 3 years(i got it used, just the tank, water, LS and LR))

 

[alix]

OK i wanted to update this. 2 of the clowns ended up dying. (they had started eating but one (the smallest of the 3) died in the net, the other 2 appeared to have gotten much better so we released them. about two days later the largest one was stuck to the filter intake, dead.) the remaining clown is swimming in the open tank now, and is strong enough to be able to swim by the intakes and not get sucked up or blown around by the jets. he is constantly hungry and eats like crazy, but he seems "lost" without the others. he just kind of swims around toward the top of the water, and is not a active or sociable as he used to be. because of this i am contemplating getting 2 more Ocellaris clowns to keep him company.
i was wondering if i my current clown could "relapse" even though he looks healthy, and should i risk adding more fish to the tank? (after QT, of course!)
Thanks

 

[reef diver]

Hmm, maybe velvet that hit the gills first(the markings) I had this happen too, never found an answer.

 

[alix]

it was strange, like the marks were a little darker than the color of the skin they were on, but they were transparent too. i though maybe the annenome got it, (CQ's dont support clowns.) but it could be velvet, i have no experience with it so i dont know what it looks like, ill look it up.