I asked about her size because sometimes it's an indicator of birth defects or someone in the flock keeping her away from feed. Chickens can be mean as crap & single out the weakest. Also the possibility of getting egg bound due to her petite size.
Like your set up. Really pretty...
I doubt you did anything wrong if you provide them good food, clean water, and a decent coop.
Was Dixie smaller? Did she isolate herself from the flock any? It could be she had a genetic defect. Was she laying? Anything abnormal about her eggs?
I think your doing the best thing to try to...