Might be worth checking your roots. I haven't had root aphids before, definitely fungus gnats, but those don't look like fungus gnats to me.
Search "Root Aphids" see if the adult flyers resemble what you're seeing.
Edit: Apologies I couldn't get a link to work. Greengeenes on youtube has a good video on them. If you search Root Aphids on youtube, it should be one of the first to show.