I can tell you for sure that your "corn like growth" is eggs from the mystery snail. I get them all the time. There is a trick to raising them until hatching. Like the apple snail, they lay eggs out of the water, but the eggs must stay wet/moist for them to develop into snails. I have a friend who raises them. She dropped the water level in the tank by about 1 inch and added an air stone and air pump so there is a constant "mist" hitting the eggs, and they hatch every time. I have yet to set up to hatch them because I would have nowhere to go with them all right now. I would say if you've seen them once, expect to see them again.