Alright, I'm working on an oatmeal stout that had an OG of 1.046. Right now it's sitting at a SG of 1.023 and it's been there for the past four days. I originally pitched safeale US-05 by just sprinkling on top. Should I pitch some more yeasty sing a starter? The only two yeast I happen to have on hand are a red star pasteur champagne and lalvin D47. Would either of these help me to get my fermentation unstuck?