Hello Everyone! I am new to this forum and new to soaping

I have been making some bath bombs and recently tried making cupcake bath bombs. They came out beautiful, but after a few days of drying the "frosting" cracked

I didn't have any trouble with it popping off as some have but almost all of them had cracks from small to large.
I am going to try adjusting my recipe, any other hints that may help with the cracking? BTW I use the typical meringue powder/water/cream of tartar/powdered sugar recipe. They are so cute, I hope I can find a way to prevent the cracking!
Also I have seen some really fluffy looking frosting - any ideas on how to get mine fluffier looking? Thanks for any suggestions!