Yellow sticky traps work well also. Something like this:
https://www.gardensalive.com/p...
In my many years of growing plants, professionally and personally, I can assure you that it only takes bringing in one little gnat on a new plant which will promptly reproduce and drive you crazy for months eliminating them. It happens, don't beat yourself up.
Like Bill says, circulating the air around your plants will help, the plants will naturally begin drawing more moisture up from around the roots to counteract the effect of of the drier air on their leaves.
