Q.Growing a spider plant baby
Why is my spider plant baby not growing?

Certified GKH Gardening Expert
Is it still on the plant, or are you trying to root it? If it's still on the plant, it will naturally stop getting bigger after a while - it's a baby, after all!
If you've cut it from the main plant to propagate, read this article and make sure you're following all the right steps:
https://www.gardeningknowhow.com/houseplants/spider-plant/propagating-spiderettes.htm
There's a chance that all it needs is time to get going.