Welcome to HCM, I have gone through you query and understood your concerns, most stools changes have a little meaning, it s could be due to some medicine ( iron supplements, pepto-bismol ) food coloring or food additives ( black Licorice, oreo cookies, grape juice, iron-rich food such as spinach and beets) bile, dark green stools can be mistaken for black under poor lighting ( Smearing a piece of stool on white paper and looking at it under a bright light often confirms that the color is dark green, another cause is a bleeding in the upper intestinal tract ( stomach ulcers and gastritis) I kindly suggest to monitoring if one of the mention above apply to your daughter, anyway a doctor should be consulted to running a few tests to discard a REAl bleeding and avoid further complications. Please kindly rate if my advise has been helpful Wishing you a good health Dr Tania Portelles-Driggs