Answer: It sounds like a fungus gnat infestation. These are little flying insects that look a lot like fruit flies. They live in moist soil and breed at the soil surface. The best way to control them is to allow the top layer of the soil to dry completely between waterings. If the plants need a moister soil and thus more frequent watering, you could put a barrier on the soil surface to keep the pests from feeding and breeding in the soil. Try a layer of sand or some decorative rocks, or for a temporary barrier, seal the top with plastic wrap. Anything to keep the adults from laying eggs in the potting soil. This will eventually eliminate the pests. If it's any comfort, the adults don't live very long. In the meantime, yellow sticky traps will also help to control the adults.
Best wishes with your plants!
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