My first flush results were the same.I was 25 y.o. then. Dark stones appeared on my second and third flushes. I did my first four flushes with two weeks intervals. That's when I saw the real picture.
Age is not really the issue here. It is all about how much you have been treated with Antibiotics in the past and how healthy was your food.
I also remember great results even though I vomited half of the oil mixture.
Those rice things you mentioned need to be examined, those can be parasites or their eggs.
Keep flushing and informing us. Good health to you!