Fresh eggs that act "old"

[sixchickstwocats]

One of our Rhode Island Reds is in her second laying season. Her eggs were fine last year. This year the whites are very thin and watery and sometimes the yolks just run out of the membrane. For awhile she was laying some of her eggs with no shells so we got some oyster shell from the feed store. They are all getting a quality lay mash as well. The egg shells have reappeared on Ellen's eggs, but the runniness makes us wonder whether the eggs are safe to eat. All our other chickens have good quality shells and eggs. We'd appreciate any suggestions - thanks!