Opinion on small flies?

Hello, When I misted my little one today I noticed some small flies moving around in his tank, what could they be and could they be the outcome of an underlying issue? Can they be harmful to my gecko?

Information on my setup: My tank was set up on the 31st of may, and is planted with live plants but I do not have any springtails or isopods. Substrate is a mix of peat moss, coco fiber and coco bark and has a drainage layer. I washed each plant before planting them in the tank.