One of my EE hens is laying 'sandy' eggs. The exterior of her shell has literal grains of 'sand' that can be dusted off. The 'sand' is in the same light-green color as her shell, and dusts off when I rub it, though the shell remains coarse/rough even after I've dusted off all the loose bits. The eggs themselves remain their normal size, shape, and when cracked open, they are normal inside. I have four ee hens of roughly the same age range, and only one of them has this extra 'sandy' deposit. None of my brown or white shell layers have this strange 'sand'. None of the EE hens appear to have any visible health problems. The birds free-range during the day with an all-flock feed and oyster shell grit available at all times. (I switched from a layer feed as I was given to understand that this will contain too much calcium for the health of my roo, and supplemental oyster shell allows the hens to take it or not as they need.) Does anyone know if this 'sandy shell' might be indicative of a health problem?