I have four hens 5-6mo. I believe my six month old hen laid her first egg yeasturday. It was perfect just a little small. This morning one of them (I am assuming the same one who laid the first egg yeasturday) laid just yolk. No shell at all. Is this normal to have incositancy like that or do u think it was one of the other hens? There wasn't Any shell?!?!