May still be recovering from topping... was that recent?
bringing down humidity will increase transpiration... I bet the plant's uptake rate of water impacted by slow transpiration in high humidity. 40-60RH% would be better... if you control environment tightly, look into VPD - at various stages there is an optimal temp/RH%.... othwerwise, i control RH mainly as a preventative measure for microbial growth, regardless of "optimal"...