Your Queen of the Night is a type of cactus grown indoors as a houseplant. The most important growing tips is to use well drained, sandy soil and do not over water. Like most houseplants this cactus will go dormant in winter when the days become shorter. This means from October until March the plant needs very little water - like one fourth a cup of water once a month. If you are watering too much the plant is more likely to become infested with mealy bugs which may the small round things growing on the plant. If you will send a photo of the round things I can make a better diagnosis. You can use a damp cloth to try and remove the small round things and determine if they are attached to the plant or colonies of white fly or even aphid. Bright light from a sunny window and good drainage may save the plant once you get the mealy bugs, white fly or aphid under control. Keep growing, Marianne Binetti