Well, I'm still not sure what was going on but...
Last night I fired up and got going. Brought it all to a boil, then added the sweet back to the drawoff side to get the gradient back. Within a half hour I was ready for a draw, much like Monday.
To my surprise, I cracked the drawoff valve and let it run...and run...and run. Pulled a little over 2 gallons, then everything seemed to run like normal.

For some reason, it just got stuck on Monday leaving me a huge first draw last night.