That mold is a harmless distraction taking advantage of an aerobic surface in the floating herbs. The point here is you are making a fermented plant extract for
nutrient availability. EM and other organisms are certainly involved as this is a fermentation but it's nothing like a true compost tea. The latter is totally about
organism diversity, brought about by aeration and rapid microbe multiplication to fill the volume with beneficial bacteria and fungi in a 24 to 36 hour brew process. What we call
brewing encompasses a broad range of purpose.
I make plant extracts in 55 gallon plastic drums. The top which got cut out (with a jigsaw) serves as a floating cover to semi-anchor down the plant material. The "stirring" I do consists of plunging down that top once or twice a day, by pressing it downward by hand, just to mix up the layers and keep any mold from forming. But if it does . . . no worries! I cover the works with a scrap of plywood to lessen evaporation and keep insect interest at bay.
Lost Nation OrchardZone 4b in New Hampshire