Vortex generators and turbulators don't always work as advertised. A lot depends on the scale of the airflow. I've never worked with vortex generators like the angled tabs you see on some airfoils but I have tried turbulators on a few different wings. In two cases I had good results and tow others I had one that made no difference and the other that made things worse.

We're talking about bandaid fixes here. A lot of things come into play. For example some inaccuracy or the level of finish on your test wing or even the residual turbulence in your airflow may have provided all the help you needed to extend the stall. And when you added your vortex generators you may have gone over the edge and it hurt more than it helped.

In his first report Michel Selig emphasized just how important the test wing finish and accuracy was and how important it was to reduce the turbulence level in his wind tunnel work on model sized airfoils.

Without knowing more about your own setup it's very hard to say if it's your tunnel, your test model or the size, placement and pattern of your vortex generators. But off the top of my head I'd suggest you try turbulator strips instead of the tab like vortex generators.