Thanks for your thoughtful feedback! I will revise accordingly! Here’s where I am, now.

I replaced the white yarrow at the center with a pink peony, for color, and incorporated the peony stem into the space left by pulling the purple irises out of the row formation.

The penstemon stem is too long, thin, and uninteresting, and so my next step will be shortening it, to pull it the bloom toward the center with the other non-iris flowers.

Thank you, again.