Hmmmm, looks rather odd for Rhodanthe anthemoides. I'm inclined to say this is a cultivar. The leaf shape isn't quite right. Rhodanthe anthemoides (Chamomile Sunray)
That's annoying. Don't think it was sold as a cultivar but I agree, those leaves don't look quite right. I'll check with the nursery. If it is a cultivar, I'll pull them out when they form seeds. Thank you.