All my discus eat, but one?

[sonicsdc25]

Lately all of my discus have been eating properly, except for 1 that's been getting skinnier by the day. What disease could this be and is it contagious and spread to my other fish?

[mattgoanna]

It is most likely internal worms or stress from the other fish. If only one gill is working it could be gill flukes. If you can move it to another tank. For worms use AZOO endoparasite tablets and gill flukes use praziquantel.