After researching the iron question all I came up with is that it is a matter of dosage. The iron needed for an adult is much higher than what is needed for a child and the dosage for a child is much too high for the daily requirements of a chicken. It is entirely possible for a chicken to suffer extreme consequences from iron poisoning.
Glad your girl has made such a marked improvement.
Jenny
Glad your girl has made such a marked improvement.
Jenny