Codensation on ceiling drywall?

Had drywall in attached garage for 21 yrs. I sealed it with oil base primer then painted with latex, also epoxied the floor now for the first time I have a condensation problem. painted and epoxy was done in August, now temps in low 40 at night and mid to upper 50's during the day and rain the day before condensation appeared (not the first rain fall since job was done) . What do I need to do to stop the condensation?