I have read people say that their specific chickens won't eat a certain thing that other people say their chickens will. Chickens certainly do have tastes and dislikes. But overall, I stand by my statement.
Two days ago, mine were fighting over a mouse they caught. I have even seen them eat raw onions out of my compost pile which most sites will tell you not to give them.
I did find that new chickens I buy sometimes won't eat something they are offered until they see others eat it. For example, mine would never eat dried corn kernels. Wouldn't touch them. Until they went and stayed with my brother-in-law's chickens for a month when we went on vacation. He grows his own corn and feeds it to his chickens. Once ours saw the other chickens eating the corn, they started to as well. And I have heard other stories like this. But yes, individual chickens will not necessarily eat "everything".
They can be a lot of work. Especially if you live in an area where they can't free-range. Though it sounds like yours can since you said they live outside. For in the coop, look up the "deep litter method" of keeping it clean. It is a lot less work. Or let them just live outside. Yours sound happy.
I think that is wonderful that you take care of those old ladies! But you might want to check the nooks and crannies of your property for eggs. Though an older hen may not lay often, they can still lay. I saw my elderly Sheila lay yesterday. But eggs aren't the only, or even best reason for keeping chickens, as you have found out.
Thank you for reading and for your comment!