I am new to brewing and just started my third batch yesterday and tasted my first batch. The first batch was a pre-hopped LME porter that came out sour. I assume this was from bacteria that beat the yeast in the sugar eating battle. I suspect it was because of the water I used, or at least the containers that I neglected to sanitize before using to top off the wort. So now for this current batch, a Brewers Best Russian Imperial Stout, I used distilled water. I read that this will leave the beer tasting flat because of the lack of minerals. Is there any way to fix this at this point? Should I added anything when I rack to second stage fermentation?