Thanks for writing. The gnats are fungus gnats and they're feedig on the peat moss in the potting mix as it breaks down. Fungus gnats aren't necessarily a problem or the sign of one, though they can be annoying.
Letting your plants dry out a little more or putting a mulch of sand over the top of the pots can help stop the gnats.
---Justin, Senior Garden Editor, BHG.com