admittedly it doesn't look great. Is that brown slime coming out of its mouth? If so its possible that it has a bacterial infection, sometimes you can also tell by giving it the sniff test, it'll smell like decomposition. I've seen a thread or two on here where people have had luck treating their yumas with Cipro, I've never done it myself so I can't offer you any advice further than other people have done it with some success. If you do treat it keep it in lower light than you normally would until it recovers. Do you know if this was a captive propagated specimen? When possible try to get captive grown as the wild/maricultured yumas have a tendency to get sick and melt in many home aquariums. They can also spread that bacterial infection to other yumas in the tank.