Photo 1 shows young mushrooms either with intact partial veils or not long after the veils have separated from the cap edge. You also see a slight roughness on the gill edges (more about this in the final photo). Photo 2 shows mostly mature mushrooms (growing on woodchip mulch), with the narrow white rings that are visible on some stems being the only evidence of the earlier partial veils. The large group of mushrooms in Photo 4 include many that, while still fresh, have faded caps. Moistening them would restore the darker colour.