I planted 4 Gumpo Whites along my walkway in 2011. Since then they have grown in width but not at all in heigth. I realize they are a low growing azalea, but they are probably not even a foot high. All that I've read, and pictures I've seen, show them to be in the 2ft - 3 ft range.

Should I / Can I prune them to get them to grow more "up"?

Thank You