kissing gourami behaving odddly?

[bugsadaisy]

hello, i have a kissing gourami in a bowl on its own for about a year and a half now( in its own bowl because it was killing off my other fish in aquarium)- its usually chasing me whenever i walk by and follows anything that moves beside its bowl but today it seems to be very very calm like( hes not chasing anything anymore- its just slowly moving in the water-like it is still sleeping appearance) everything is fine in the fish bowl filter, heater are o.k. and water is good, the fish usually eats all its food but is not even interested in it today. the change in behaviour has occured overnight. fish is not gulping for air from water surface but is swimming very close to the water surface. has anyone any suggestions on why the fish is less active(its still alive)??and what i can do to fix things. i have a seperate aquarium of tropical fish and have never seen this type of behaviour before.