Got new gas cooker and now my cupcakes seem to shrink after they out of oven and go wrinkly? What's happening ?

-You're oven is too hot, you need to turn it down a bit. All ovens are different, even though you probably use the new cooker on the same setting as the old one the temperature won't be exactly the same. It always takes a bit of experimenting to get used to a new cooker.Bake them at 25 degrees less than what it calls for.