tasty looking boards!
not sure about the haze, could be outgassing from core or expansion of tiny bubbles in the layup form heating too early as you said, or something else. If your shop is unheated or
unevenly heated or materials stored cold, could condensation be a factor?
I would say make sure everything is temperature controlled and layup at a falling temperature, until resin has gelled, then ramp up heat. Pros program their ovens to heat gradually, sometimes over a few hours, hold postcure heat for some hours then ramp down slowly... You could do this with a computer, tweaking a thermostat, or opening/closing vents on a hot box.
I have only done things the low tech way, but I like to warm everything up especially the resin (but not much, just to 80 F or so) then cut on the AC while glassing.