So, I think the yeast developed quickly due to the warm temps and the fresh-ground wheat. It's been colder the last two days, and the starter has slowed way down. I've also converted it to just white flour so I don't keep introducing new yeast from the fresh ground stuff as per sourdough.com recs. I'm only establishing a small amount of starter (4T) until I reach the fridge stage, then I will up it to a full cup and refrigerate it. Does that sound right?
I've also named it Wentworth.
One more thing I've been wondering. I've read that temps above 95 degreesF will kill the wild yeast, but sourdough histories keep talking about Egyptian sourdoughs. Surely the ancient (and modern) sourdoughs of Egypt experience really high temps and survive?