Im new to wine making and have 3 gallons of a white grape wine that seems very bitter and not very strong. I racked it into 3 1 gallon bottles and have it air locked. I am wondering if i could add more sugar and new yeast and try to increase the alchohol level. Is this possible? i did not get the SG initially so im at a loss right now. I may just have to chaulk this batch up as a loss.