Unhealthy siamese fighter

[Deepblue02]

In the last few days I have noticed he just sits in one corner of the tank down on the gravel. He doesn't look bloated or anything, just sat there, he will move about an inch and then sit there, is he ill or sulking about something? Any ideas?

 

[Mumma.of.two]

What are the ammonia, nitrite, nitrate, pH and temperature of the tank? Water change schedule? Tank mates? Tank size? How long has it been set up for? Any change to the filter or substrate recently?