Since Nov it's been fluctuating between 5-7 ug/mg, with a few spikes hitting 9 and 10. At this moment its a 6.

I haven't checked the TDS but when I used a water test strip for an aquarium early this year it was in the hard water range.

Thanks to this post, I checked my ultrasonic filled with tap water. With it running all night in a bedroom with an open door, morning pm2.5 readings are ~30 and the meter is in the kitchen.