my starter is about three weeks old, give or take a few days.  I've baked twice with it, and although the leaven "floated," I simply didn't trust it to completely do the job of adding air to my bread, so I cheated with a bit of yeast.  Today was supposed to be my first yeast free bake and, after messing around all week with flour percentages (whole wheat, AP, rye, tile grout - just kidding on that one) and weights of the actual starter (30 grams, 60 grams, 60 grams and so on) last night I made the leaven according to the tartine country bread recipe and this morning, 10 hours into it, I attempted to get the starter to float.  It sunk like it had on cement shoes.  should I again resort to supplementing it with a bit of yeast and swear to never mess around with my starter formula again or give it a couple of hours to ferment a bit more?  Will that make a difference?  Darn.