These are probably fungus gnats hatching out in the potting soil. Your plants are sitting in saturated soil which will rot the roots. You need to repot your plants in soil that drains faster. You can add very coarse sand (REALLY coarse sand or some that has small gravel), pebbles, bark chunks, perlite, even broken up packing peanuts to the bottom portion of each pot. Not added to the surface. Also, enlarge the pot's drainage holes and keep the pot saucer empty. Unfortunately, your soil is now full of gnat eggs so you won't get rid of them until you replace the soil. The gnats aren't dangerous, just really annoying!