We nursed a sick chick in a similar situation with a dropper and making our own electrolyte water (get the tecipe online, it's easy). We fed her every hour or two or more depending on what we were doing. She is over a year old now, smaller than the other hens and slower with some misshaped...
I use New Country Organic feed and have the best eggs I've ever seen, very hard shells. My hens are very healthy. The feed is actual seeds. I also supplement with oyster shell and give them high protein treats like split peas and lentils. Their favorite is raisins. This is not an inexpensive...
Treats every day like chopped greens, squat down so you aren't towering over them, feed out of your hand, and when you bring the treat make the same noise every time (consistent call). Different birds have different personalities. Some will hop on your lap, some never want to be touched. Simple...
I too have thin hens, ISA Browns. I feed them as much as possible. They don't seem to like the cracked corn as much as the scratch with other seeds in it. They had their beaks cut before we got them, and it's very hard for them to pick up little pieces. They can't preen themselves either, and...