Here's wingleaf primrose with typical healthy leaves. But notice the petals. This angle was carefully chosen so that you might overlook the missing fourth petal. That is a serious problem for photographers. Like many of the related evening-primroses, these open at night. In the morning, these very soon drop their petals. You have to get there early, on a windless day. And remember, never touch! Resist the temptation to adjust anything. The slightest movement will jar the petals loose. I don't remember if that happened here, or if the first petal had already fallen.