I was giving them a modified GAPS diet before. So, I was very strict with what we had in the house. Before GAPS, I only ever had home made things, not much store-bought stuff. During that GAPS period they would eat what I had at home, except the youngest one, who would eat very little of anything, and they would all go crazy when they were around other food (at friends, parties etc). I guess I was worried they would be permanently in party mode if I had that kind of stuff in the house, but they seem to be happy to take it or leave it and eat a range of things.
I wish I knew what to say about your little one who eats such a small amount. My littlest one still generally eats what I think is a very small amount but it’s still more than before. If you think it’s a power struggle, perhaps you might need to just be completely nonchalant about what she eats and not notice how much or coerce her at all. I don’t know. Do you think there is a reason for her small appetite other than it possibly being a power struggle?