pH- 5.8, sounds great!
Your old meter's electrode is bad. Depending on the make/brand of your unit, you may be able to replace it and have two working meters. However, I would recommend a Blue Labs or Hanna non-pen-type unit if you plan on making this a big hobby
. That pen should be fine if you're just doing your own head stash grow. Just make sure to store it with storing solution.
But in my experience:The pen's are always finicky, and the electrode's usually cost half or more what the whole unit does. I used a pen for my first pH meter. Never getting one again. But it did last me a few years with calibration/storing it right. It's worth the extra money in the long run to get the portable, but non-pen pH units (for me).
I'm still trying to figure out which is better: Blue Labs or Hanna. The fact that Blue Labs made in USA is kind of a nice thing, but they are a bit pricey. But that's a different subject lol.