Now that she's laying, i had different questions.
Are double yolks common? Every one of Doctors eggs so far have been double yolks.
Blood spots- what do they mean?
How can you tell if the eggs are fertile?
The blood spots are just tiny pieces of lining from the reproductive tract. You can just pick them out. Double yolks are common in birds that have just begun laying. In a fertile egg there will be a lighter yellow bullseye on the yolk.
I never knew that the blood spots came from the reproductive tract! dianaross77 is correct about the bullseye.
ETA: My chickens who are just starting to lay also are known for laying doubleyolks. Yum!