Her backwardness may be not because she is slow to develop, but because she soon exhausted her capacity for developing'.

她的落后可能不是因为她发展缓慢，而是因为她很快就耗尽了发展能力。

The solution is now staying pink which means that I've exhausted it's buffering capacity, and the pH has dropped below the indicators end point.

该溶液现在保持粉红色， 这意味着我已经耗尽了它的缓冲能力，并且 pH 值已降至指标终点以下。