I often recommend a Pedialyte bath for frogs that aren't eating, as it can stimulate appetite, but I have no experience with Xenopus genus frogs. Another user posted this a while ago.
http://www.frogforum.net/showthread....ulate-appetite
In my reading, usually a 20 minute bath is recommended, so if you worry an hour is too long, you can try a 20 minute bath instead. Typically the mixture is around 1 part UNFLAVORED Pedialyte(the flavored kind can be harmful to frogs) to 9-10 parts dechlorinated water. I've seen people recommend rinsing them off after the bath, but I'm not sure how you'd that for an aquatic frog.
As elly mentioned, quarantine is a good option. Even if it isn't infectious it is better to be safe than sorry. Good luck, I hope your frog feels better.