The other day my mum boiled some of my 3yr old RIR's eggs and when we cut them in half, the yolks were all swirly, the colours were yolk colour, but light yellow and her normal orange yolk colour swirled together. Mum didn't trust them and fed them to the dogs. The RIR is the only one laying at the moment, my 1yr old mutt is being broody on nothing (she may sit on my RIR's daily egg for a few hours) and my plymouth rock is busy raising her two chicks and hasn't started up again yet. I do not have a rooster. Just wondering what would cause this, her feed hasn't changed lately other than them getting shell grit now...I have pics and will post if need be later.