Yes it's natural but it;s caused buy an excess of nutrients snails dyeing and decaying will add to the problem IMO
your feeding way to much I have 7 fish,12 hermits and countless snails and i dont feed that much. My rule for feeding is there stomach is only the size of there eye
Try 2 pellets every day Use a turkey baster to suck up the cyano
don't stir your sand as it will make things far worse. Use a red lens on a flashlight 2-3 hrs after lights out you should see those snails out then.
Most people create their own problems by not following the basics and refusing to stock appropriate to their system. Gregcoyote 2013
SPS = Stability Promotes Success