When it was suspected that Jax had a back issue, the ortho tech made the comment that the whole back should have been xrayed. Ortho's have more experience looking for inflammation, disk space issues, etc.
The xrays look like decent positioning. Probably about the same as Jax's hips (mild).
I would personally wait for the radiologist to review. But would make an appt with the ortho in the mean time. It might be he just needs to go to a chiropractor for a pinched nerve from doing agility and twisting wrong. Is he on any anti-inflammatory?