I know this is from 4 months ago but I am interested also. I would love to get my hands on some Ayamm Cerami/Easter Egger crosses as well. If anyone knows anyone who sells hatching eggs or day-old chicks of this kind of cross, let me know.
I think your darker one may be single barred (B/b+) and not B/B which is what you want for a golden cuckoo. If you keep the darker one and he is indeed B/b+ then half of his female offspring will be unbarred.
My theory also makes sense with you saying he looked like a girl chick. Girl GCMs are...