The sourdough that I have was vialated, when someone mixed their pancake batter in the "Mother Pot".  I have been working to save it since.  I removed all foreign ingrediants I could see, and have been scraping mold since.  Now it is to the point where I can cook with it, but after I fed it last night it hasn't come up yet today.  Any advice?  Would yeast now, or ever, be a good idea?