Those are definitely a two spotted spider mite IMO. They are fairly common, but difficult to get rid of completely. I’ve never had to deal with them personally, but my dad got them and had to completely reset his grow. He got rid of all his soil, plants, etc, bleached and sprayed everything with isopropyl alcohol, then gave about two to three weeks of spraying alcohol every two to three days.
You did one treatment of neem and that’s not near enough to stop them, it simply slowed them down a bit. You can try a neem/kelp tea on the soil to slow them down, and maybe finish up your current harvest. You can also try the Method-1 PPS (I would be happy to send you some).
The real question is how did they get there in the first place? If you don’t sort that out, they will just come back. If you never brought in any clones or other plants, it has to be coming from you possibly from your yard. You will need to be extra cautious to shower and change clothes when working in the yard before touching your plants.