Your birds look nice and healthy in the pics, although I can't tell about thin-ness with those feathers. The fact that they ate all that grit is a sign that they needed it (despite what some of the feedback on here has said that chickens don't need grit!). If you feed soft foods or foods that don't need to be ground up, I believe you don't need grit. But my free-range chickens eat all kinds of seeds and whole grains (in their feed) that must have grit to digest!
By the way, you sound like a weston-pricey person, and I love the fact that you're feeding your chickens organic foods. Despite what your husband says chickens do not need medicated feeds -- how does he think our grandparents raised their chickens??? They just need a balanced feed that provides them with the right nutrition. I love Carla Emery's book called "The Encyclopedia of Country Living" because it describes how to make home-made feeds for all animals, including chickens.
I don't feed medicated feeds, never have, and there are some people who say medicated feed can mask an unhealthy flock because of poor housing conditions or disease, because the medication (antibiotics) keeps them going despite their conditions.
I feed my chickens a custom-mix I buy from a local organic farmer who grows much of the grain himself. It has corn, roasted soybeans, and oats along with minerals and probiotics that he buys from Fertrell Company (organic feeds). He grinds half the grains, but only cracks the other half, so the feed has both powder and grain kernels in it.
By the way, although chickens love milk, I would be careful how old the milk is -- from what I've read, you should never feed chickens old vegetables, rotten items, etc. because of their small size, it can really hurt them or make them sick. They are not like Pigs which can eat anything even if it is old, curdled, stale, and rotten, but chickens and rabbits are different.
You're doing a great job, and I'm sure your chickens will be fine!
By the way, I love the fact that your girls are so political that they decided to hang a poster in their coop! :