Death Layer/ Egyptian Fayoumi Chickens ?

[McChooky]

I ordered and hatched several death layer chickens. Now that they are older just one of the hens has a regular cone and not a rose comb like the death layers, she looks like a Egyptian Fayoumi. Is it common for death layer chicken to occasionally come out with a regular comb ? Or do people cross them sometimes or maybe one got mixed in with my eggs? I want to stay selling their eggs and chicks but want to make sure what is going on. Thanks for any help!

The Möwe also comes in the same colors (Silver pencilled and gold)