Appreciate the input. Just a friendly reminder that we're not using the 5e leveling system. We're using the milestones set down in the AP, which very well may be part of the problem.
Many thanks to everyone for all of the extremely helpful input. Some great ideas in here re: how I can slow things down a bit and some validating info telling me that it's also just the nature of the AP. Will be putting all of this input to good use!