That’s an ornate leopard wrasse transitioning male.
That said, they’re notorious for internal parasites — it’s possible he’s had them for a while but they may just now be causing trouble.
Feeding foods soaked in metroplex and focus would be the way to fix this (if that were the problem) but he’s not eating. So, a hospital tank with metroplex dosed would be a second option and it would also treat any underlying hidden infections should they be an issue as well.
Leopards not eating isn’t a good sign,