red ring in boiled eggs

could it be the red stained maggot treat they had?

Any chance they were fertilised?  Only I remember when I used to incubate eggs that some of them had a red ring which meant the embryo was dead.

Just a thought

Were they Ruby rings ?

I did find a curtain ringf in an egg, a long time ago, though and that was in a boiled egg, and that isnt a joke, the wife and kids were there, before the internet was in full swing, so I couldnt google it, but the vet said it was possible, but he had never heard of it