Certified GKH Gardening Expert
It is not a cause for concern. These can happen from time to time, more often depending on variety. They are just extra petals, and sometimes an illformed twin flower. They may, or may not bloom. They will often fall off as well.
This article will give you more information on the care of these plants: https://www.gardeningknowhow.com/ornamental/bulbs/gladiola/care-of-gladiolas-how-to-grow-gladiolas-in-your-garden.htm