Why don't you go to the "images" section and see if what you are passing looks like any of those pictures. They sound like parasites to me.......which makes it super cool that you are passing them!!! Oh, and yes, you can continue to pass stuff after your flush---you have proven that!!
Keep flushing until you see no more stones 2-3 weeks apart.
I guess the best way to describe chaff----if you have ever been sunburned and your skin starts shedding or sloughing off---know what that looks like? Chaff kinda looks like that.