Question on growing Red Phlox flowers?

21st Century Red Phlox flowers after they're planted seem to flatten out and look like some animal slept on them overnight. This same appearance seems to happen at the store where they're bought as well. After a week or so, the red blossoms and stems flatten out and look like they're dying. I asked the people at the florist and they don't know why either. Is this type of flower susceptible to cooler weather and reacts like this? They're being watered every week and in about 75 degree weather.