What Could Cause Bleeding And Black Stool A Week After Tonsillectomy?

Good evening! My daughter has a tonsillectomy after 8 days she had a bleeding and she had and urgent surgery where blood has been stopped and pieces of her tonsils has been removed. The second surgery had taken place in the 31 of August. From that day she has a black stool (3 times), the pasta one today (5 Sept) is it normal?