I'm a couple of hundred miles north of you, but during those really warm days last week with temps pushing 90F, the hive on the platform scale was posting gains of 5 lbs. a day. And this was before the fruit trees bloomed. Granted, it is a mature colony, but it just shows how much the bees can do in a short time, if the weather cooperates.
It sounds like you have a good strong colony and that they are moving to natural sources on their own, but either way I would wean them off of the syrup about now.
“If you want to gather honey, don't kick over the beehive.” - Dale Carnegie