My chickens breeds range from Buffs to Easter Eggers to Black Copper Marans. My egg yolks are not as dark and rich looking as I would like, though they still taste fantastic. The girls are fed a very good balanced diet, free range in a very large yard area and are fed occasional scratch and kitchen scraps. I would love to improve the look of my egg yolks to a nice golden yellow to orange. Does the breed of chicken have to do with this or diet only? what can I do to improve the yolk color? Thanks!