I really haven’t seen any specks in the fertilized eggs..? We collect eggs daily but I would imagine if you missed any for 1-2 days and a Brodie hen sat on em then yes there would be some blood. Could be some blood and other interesting things. A fertilized/incubated egg hatches a chick in just 20-21 days so the growth rate is incredible. But as for specks we’ve always had roosters and no problems. One thing I found ‘crazy’ happened a few years ago. A friend of ours wanted some fertilized eggs for incubating so we gave them 5 dozen. The eggs had been on my counter top for 2-3 weeks already when we gave them to them. They kept them at room temp on their counter and brought them to a farm in Mexico several weeks later and incubated them there. Said they had like 90%! Hatch success. And all that after more than a month of sitting on a counter.