Here is a picture of him
While that looks like a spinal injury, it may not be that, especially with no apparent damage to its snout. When I see a new yellow coris bent like that, but still trying to take food, I feel that it is pretty safe to conclude that it is UNWD:
Unknown Neurological Wrasse Disease (UNWD)
Unknown Neurological Wrasse disease (UNWD) There is a disease that afflicts newly acquired wrasses, usually Cirrhilabrus fairy wrasses or flasher wrasses, Pseudocheilinus, but occasionally other species as well. The gross visual symptoms are always the same; the fish shows a rapid onset of...
www.reef2reef.com
Sorry, but this has no known treatment and is usually fatal.
Jay