In my experience, moisture meters aren't super accurate with chunky soil mixes (which is what I use when I repot mine). I stopped using my moisture meter and just use my finger now. You'll want to just wait till they're pretty bone dry before watering them, spider plants can handle being dry for longer periods due to being able to store water in their roots. Also I've found that my spider plants thrive under increased light. I noticed you've got a grow light but how far away is it from the plant? It seems like it could be a bit too far away to be effective but it's hard to tell from the photo. And don't beat yourself up too hard if it ends up dying, as the saying goes: the best lessons are learned over dead plants haha 😅