I just got a handful of those primrose plants that are available this time of year and brought them home. They were a bit dry, so i watered them thoroughly and have kept them damp. Of the five plants Ii bought (they had partially opened flowers when I purchased them), only one has properly opened up. The other four have lots of flowers, but they won't open and they are on their way out. It's been a week now and I just don't get it. I get these flowers every year and never had a problem like this. Any ideas?