Karl Forester grass
Hello, These plants look like they were just planted in July as you say. Perennials require time to allow their roots to grow after they have been first planted. They do that in their first year, when you have provided them with adequate water and appropriate conditions, in the case of Karl Foerster feather reed grass that would be a sunny location with well-draining soil. Once their roots are established, they will send up those lovely graceful stems that you want. I suggest you care for them this fall and next year you will see the plant grow with the stems that you want.