It is possible you are seeing the perennial form of annual bluegrass--some of it survives the winter--it persisted through the winter, instead of arising from seed. I don't know about the henbit. Are you saying you used pendimethalin, and then prodiamine? At label rate? Was your spreader calibrated accurately? Was the green color uniform in the fall? No skips or stripes? What was the condition before you started? You may be looking at 95 percent control--if Poa was heavy in the previous year. What were them high temps when you treated? How do this compare with university recommendations for your state? Dealer's suggestions?