When the mushrooms leave there primordial state, they are maturing to reproduce.
You can recognize this state when the veil connecting the stem and the hat is tearing or just torn (see image).
Do not wait much longer and pick the mushrooms.
When you are too late picking the mushrooms, the mushroom will drop its' spores.
All the mushrooms and the grow bags will turn black/purple. This looks just icky, but is harmless.
Mushrooms will loose some of the potency when they drop there spores.