What happened to my tang???

[davanti]

I woke up this morning and my yellow tang(about 5-6 inches and the coolest color of yellow) was stuck behind the live rock. He couldn't swim, and started getting red on his sides like he was bleeding from the inside. He and my three striped damsel both died by tonight. My water is fine, it is a 55 gal. with about 30-40 lbs of live rock, and besides the tang and damsel is my maroon clown(thank God she is still alive)

 

[nicetry]

Please post as much info on your tank as possible; All water parameters (saying they're fine doesn't tell anything). I'm interested in your pH, as low pH can bring about the red streaks you were seeing. How long has the tank been set up, how long have you had the fish.
Had you noticed any other symptoms; labored breathing, twitching, glancing off rocks, etc..

 

[davanti]

My pH is 8.3 the specific gravity is 1.024. My tank has been set up for four months. I have had the tang for about 5 weeks and have not had any problems. He did not eat the seaweed the night before. In the morning when I found him he was not moving and appeared to be stuck face down in the sand. When I got him out he went straight to the bottom and stayed there. His breathing was very rapid and he kept moving his fins even though he was stuck on the bottom. Later he had moved to the other side of the tank but still on the bottom then died.

 

[nicetry]

Assuming there was no detectable ammonia or nitrite, the fish may have been ill. Sounds like a bacterial infection, possibly secondary to parasites. This could account for the rapid breathing. Bacterial infection can also bring out the red streaking.
I'm curious as to why the damsel died though, being a hardy fish. Is the clown acting okay? When did you add the clown?

 

[davanti]

The clown was my first fish, shortly after came the damsel who did have a bacterial infection about 3-4 weeks before I got the tang, but after treating the damsel I have not seen any signs since then, and the clown has been healthy through everything.

 

[davanti]

OH I just remembered about the past two days the tang has spent a lot of time swimming against the current of the power head, which he usually did not do. I do not know if it means anything.
thanks for your help