Not sure how that's badly balanced? Four of the eight are in the 320's range, while the other four are barely outliers, two above that in the 330's range, and two below in the 310's range.
Like yeah, you could cherry pick the highest, yellow at 336, and the lowest, red at 311, and go 'That's a 25 girl difference!', but like, with the sheer number of girls there are, over 2500, that 25 girls means the highest only has 1% more of the total than the lowest.