Compost problems are process problems. No spray corrects moisture, pH, nitrogen or air distribution, and anything applied on a mushroom farm must be checked against its current label approval and state rules before use, not chosen from an old note book.
So the next step after a diagnosis is a measurement, not a chemical. Change one thing in the limiting domain, record what you changed and why, then look for the response in the same measurement. If the response does not come, your cause was wrong and the record you kept is what lets you say so.