have you had him long enough to know his personality & how he reacts to "change"?
He might be sulking because of lights being different.
might have stuffed himself on feeders and be chilling, not interested in pellets too.
My O acts like a brat after he stuffs himself on special treats, loses interest in pellets.
He randomly sulks about changes or disturbances, not every time.
He's been sitting around bottom of tank all day today. I may have "bothered" him during water change last night.
If it's an illness caused by feeders you should start seeing other symptoms.
+1 to all of that. I wouldnt be surprised if the feeders just spoiled him.