Humidity is strain, cola size, and light sorce dependent .I realize It's hard to control in most greenhouse setups but 38% is to low at any stage under any light for an extended period of time. Terpenes and flavonoids volatilize below 50% even before the chop. Just a day or two at 38% probably won't effect quality much though. After harvest 38% is a massive no no. 50% to 55% under hps, and natural light in late flower. 55%-60% under LED. 24 years, 365 days a year coco coir and organic chelate experience. If your getting mold between 50% to 60% the plant has poor mold resistance.