MistyDSnakes

Hello everyone, so I have recently encountered an issue where I have what seems like tens to hundreds of these tiny black bugs(sort of resembling fruitflies), flying around the inside of some of my enclosures. It is only an issue where I have mulch/eco-earth fiber. The eco-earth to me, seems to be bringing them out but I can't understand why all of a sudden? I have not changed to any different brands, my cleaning techniques have not changed recently, everything I have is kept nice and clean, there are zero feces, zero spoiled food etc. Can anyone tell me what may have caused these to just appear one day and what I can do about it and to avoid this happening again. Thank you all for your time.