If the conditions are too moist at the point where mushrooms enter their last fruiting stage, some mycelium can grow on the stems.
If the conditions are too moist at the point where mushrooms enter their last fruiting stage, some mycelium can grow on the stems. Generally it doesn't do any harm. You can try to lower the humidity a bit by providing more fresh air, but in general the condition isn't something you should be too concerned about.
