Certified GKH Gardening Expert
This is normal. These plants can reach anywhere between 2-6 inches in height. If they are getting unsightly, you can cut them back some.
I have some of these in my zone 5 rock garden. I have a handful that are doing this very thing this year and from what I've read its normal, it is the mother plant flowering before she dies. she leaves us with many chicks No. If she becomes unsightly you can pluck her out and it will give the others room to grow.