Answer: Based on your description I am wondering if somehow fungus gnats have been introduced. These resemble little fruit flies and they breed in damp soil. They can be controlled by making sure you are not overwatering so that the soil surface is not kept overly wet (since you have grown these plants for years I doubt you are overwatering, but this can be a problem); placing a thin layer of sand or fine gravel atop the soil to create a quick drying layer at the surface; or by applying a product such as Gnatrol labeled for control of fungus gnats. You will see results in a week or two once the breeding cycle has been interrupted.
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