I am not an expert on schizoaffective disorder, but I do believe it's worth mentioning to your therapist and then see what he/she says. I know losing interest in things someone once enjoyed can be a sign of depression. From that response, then you would get an idea about whether to tell your psychiatrist. It wouldn't hurt to bring it up. They do need to know about behavioral and mood changes.

Are you aware of anything that happened in church or even in your life that might be turning you off to it?