If those are what I think they are, then they feed on rotting material. If that is the case you just need to keep the dead leaves from sitting around. keep the grow clean of organic matter. You can use neem oil on surroundings just not on the flowers, as a preventative. If you need to use it on the plants, I recommend that you get Azamax, which is derived from the active ingredient in neem oil. The Azamax seems to dissolve in water better which makes it absorb easier. You can give the Azamax solution to the plants through the hydro system or directly into the medium. This is known as a drench. The plant will absorb it and move it throughout the plants' leaves. This will make it effective as a deterrent to some bugs and deadly to other bugs.
The Azamax being organic will be metabolized by the plant within 10 days depending on strength. As long as you stop using it 2 weeks before harvest, you'll never taste it in the buds.