Some growers who apply MycroNutrient between flushes and have some large mushrooms left (as above) may see a slight white colouring on the cap edges the following day. To avoid this apply 1/2 L/m2 clean water after the supplement application which is just enough to wash off caps, but not any more as we want to keep the nutrient in the pinning zone for a period to react.
This is not normally an issue with small pins.