These are either fungus gnats or white flies. Shake the plants and check to see if these little bugs fly up and the down very quickly, look close on the leaves for little skinny white bugs that will not appear to look like anything. If you see these then you have white flies. No pest strips kill a lot of them but if they have laid eggs then they will re-appear. Get safer soap and spray when light are off, under leaves and on top. You may have to do this a few times. Once bugs are gone, spray plants with water.
Like said above, some bugs will live in the soil. If a small grow-few plants, cover soil.