I found a troupe of three generations of these agaricus on the lawn of a local supermarket. The large one with the very dark brown gills is from a first flush, the ones with the tan gills (which were pink this aft) are from a second and the ones that don't have flattened caps yet are the third flush. They don't stain when cut and the spore print will be obviously brown, and the caps go a little coppery yellow where rubbed. Thanks for your ideas about this. Fish Dr.