Hi there, and welcome!

The stix only have a shelf life of about 6 months after they've been opened. It does sound as though yours are outdated.

Personally I never bother with the things. They can be inaccurate for many reasons, giving false positive and false negative results. So I would just carry on with your plan, and worry about the weight, not the stix.

You'll find more info about ketostix in Low Carb Tips, on the orange bar at the top of the screen.

Rosebud