i find myc growth fascinating as well, and what you are seeing is the result of multispore inoculation, where you have a bunch of genetic individuals competiting for substrate. the agressive ones will develop a better myc network and be better able to support fruit.

if you're into this shit, you should look into doing some agar work. multispore inoculatoins on agar allow you to select the more agressive myc (or whatever trait you want in your myc) and to develop your strain how you want it. look up RR video "let's grow mushrooms" on youtube