Marilyn, I had to do this once to my entire semp bed. I just used a hand weeder (like a hand crow bar) and lifted the semp heads gently and shoved dirt under them to elevate them. This is probably not as thorough a job as pulling everything out and making sure that your elevation is neat, level and thoroughly packed but if you don't want to pull the more established plants out, you can resort to this.
If you do pull stuff out, just make sure to get a big chunk of the dirt under and around the plants too so as to minimize disturbing the roots.
Good luck!
