I've been working on this story for nearly 4 years, and it never occurred to me to double check that my events were lining up with the lunar cycle in 1993 until I was coming home from some shopping today..major writer's failure on my part. SMH.
I have since updated Ella's birthday to be on November 19th to smooth things over as much as possible. I am taking the creative liberty to move back the Gryffindor Quidditch match to the November 27th, 1993 to coincide with the full moon recorded on November 29, 1993.
The perfectionist in me hates messing with canon, but as it was pointed out to me, Ella already messes with canon. Moving back the date of a sporting event isn't actually all that significant in comparison...