Yes. Yeast metabolize nutrients at different times throughout fermentation. Dosing nutrients at the most optimal moments can enhance yeast performance. As fermentation progresses and the ethanol level rises, yeast becomes less and less able to assimilate nutrients. For this reason, each nutrient has been created for specific addition times. For example, GoFerm has been designed to add during rehydration. Other nutrients like Fermaid K are added at one-third sugar depletion and never into the rehydration water.