Rworner, both the temperature of the dough and the sugar content will impact both the top and the bottom of the skin. If you reduce the sugar, the bottom will brown slower, but so will the top. If you turn up the fridge temp or let the dough warm up longer, the top will brown faster, but so will the bottom.
There's a small chance that your top/bottom browning issue is recipe/dough management related, but I think it's more like related to your oven.
Is your oven gas or electric? Model? Deck Material?
If gas, when was the last time you cleaned the ducts and air entry points?
Could anything be obstructing the flue plates?
If gas, is the oven properly vented? (no long horizontal runs, tees, elbows)
How long have you had these ovens for? How recently did the top coloration issue arise? Do you have a photo of the pizza (or a link to a photo) from a time when it was baking to your satisfaction and a photo of the problem?
Do you own an infrared thermometer? If so, what temps are you getting from the hearth, ceiling and sides?