I started out with an already laying flock of chickens. After purchasing them I decided I wanted more so I went to my local Tractor Supply and bought a couple black sex-link pullets. They're about 15 weeks or so now and I think one may have just laid its first egg. But the egg is really small so I don't know what else to make of it. It's obvious the pullets aren't full grown yet when comparing them to the other hens I have. Is it too early for them to be laying already? Is this because I've been allowing them to eat the egg layer feed with my other hens for the past month? Please look at the picture below. Any advice would be appreciated. Thanks.