Fungus Gnats???

Hi guys, having some probs with these little critters, could anyune please tell me what kind of damage they can do 2 my plants,
at the moment i am having probs with what looks like IRON def... all the bud sites are fading in color, could this be cause of them damn flies?.....

please help as i am losing all hope,
thanx in advance.

pics will help but spider mites do leave white spots...sand helps kill eggs and a spray would help the plant

It is not the flying gnats that are the problem, it is the larvae. They eat your roots. Add so GoGnats! or SM-90.