The Christmas Cactus like some sun, not much direct sun when really hot, they like to be left dry in between watering. If they feel dry on top it does not always mean they are dry on the bottom so stick your finger down in the soil and be sure they are dry. Then give them a good drink.
They will be fine. They need to have at least 11 to 14 hours of darkness each day, for a few weeks before they will set buds.
