Sounds like the BlueLab needs a proper cleaning.
My pH pen, EcoTestr by Eutech/Oakton was really slow to stabilize so I used a 2-part cleaning sol'n on it and now it's really fast in comparison.
I rarely use my pH pen and it had sat on the shelf bone dry for about 3 years. It's at least 7 years old now and after soaking in storage sol'n for a couple days before using again has worked fine.
I buy the pre-made liquid calibration sol'ns in 4 and 7. Same for the ppm pen tho 1000ppm.
I also keep the pH pen on the same spot on the top shelf in the grow room so I never have to go looking for it.