Sick Clown - Need Help Fast

My clown fish are sick. I have (had) two. This one had a white rough area on one side (see photo below). My other clown has a sore behind one of it's pectoral fins. It also has the lower part of it tale fin that is missing. I fresh water dipped both of them for 10 minutes. I have the surviving one in a hospital tank and have just put the first treatment of Melafix in the Hospital tank. These fish have been healthy since I introduced them into the tank. I am puzzled. . .

My main tank is 90 gal. Tank mates are: yellow tang, tailspot blennie, coral beauty. I have recently added a harlequin shrimp to help with those pesky star fish, and added some snails and a couple of conches to help with tank maintenance. My tank is 1 year old. These clowns have been in the tank for approx 9 months. I have had no previous problems in my tank with any other fish. The two clowns stayed in the torch coral 100% of the time. My other fish are not showing any signs of problems (at least that I can tell. . .) I have recently changed my lighting from PC to MH.

Does anyone know what this is that is on the body of this fish and what I should treat with?

 

it could be Brooklynella Ich based on the coloring and presentation but I'm not sure from your picture resolution.
When did the symptoms start. Freshwater Dips are extremely shocking for a fish and will probably kill both. I would try to feed this clown with it's normal food source soaked in garlic. If you have a cleaner shrimp, or wrasse, or can get one quickly I would put it in the QT tank as they will clean Ich.
Before you start treating a sick fish next time post here first with pictures.

 

Update

Thanks for the advise on the cleaner shrimp. I used to have one in my tank. I took it back to the LFS because it was harassing my corals. The clown doesn't seem to be getting any worse that I can tell. And, none of my other fish in the main tank are sick . I still have the clown in the hospital tank.

If it is Brooklynella, what other remedies should I use (other than cleaner shrimp)? What other signs should I look for to confirm this diagnosis? Or, is there a website that would show photos of other fish with this?