One thing that bugs me is the current state of the aqueduct-hospital-medical lab buildingchain. While they are mathematically balanced in terms of growth-increase, the time they are unlocked is not taken into account. Hospitals will have less effect than aqueducts simply because they come at a time when most of your core cities are already developed and when you get one up in a new city (after aqueduct and more important infrastructure) the city will already have grown quite a bit.
The medical lab is even worse, since there are no food-boosts anywhere this late in the tech tree to take advantage of (aqueducts have civil service, hospitals have fertilizer). My suggestion would be to increase the hospital effect (maybe 40% too) and give a new, more direct effect to the medical lab, like population increase in all cities (similar to the hanging gardens, but with increasing costs for number of cities, if needed for balance).