The two factors that initiation pinning are light and carbon dioxide/oxygen concentration.  During incubation you want the mycelium to be in complete darkness with a temperature close to eighty degrees fahrenheit and once the substrate is completely colonized that is when you want to initiate fruiting by exposing to natural/artificial light and start fanning to get the carbon dioxide out  and oxygen in the grow box.

If any one these two variables are implemented too early the mycelium could start pinning prematurely....I'm guilty of this my first grow I was looking at my pf jars multiple times throughout the day.  Aint nothing slower than watching mycelium grow!  Good luck sounds promising so far!