Yesterday I brewed a Belgian triple with a target OG of 1.084. My efficiency and volume were a little of and I ended up with about 5 3/4 gallons of 1.075 wert. I also mashed a little higher than expected (152ish vs 150 for 75 minutes). My brewing program is telling me this will attenuate to 1.021. Should I add some sugar (sterilized) in a day or 2 to raise the OG and balance the bitterness? If I do is it best to use corn sugar or something else that will give me some residual sweetness?