Yellow tang help

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Picked up a nice 3 inch yellow tang a week and a half ago. He's in 65 gallons with 2 small percs, a hawk fish and a watchman goby. Well the tang ate well to begin with and is still eating but has stopped swimming around and has a very bloated stomach on both sides. Have fed a mixture of blood worms and brine and spurlina flake. The other fish are fine and water is stable. Any ideas???