Hi Llewanda, there would be no contraindications with the minocycline. Remember to evaluate this dog for a simple Wind invasion (e.g., causing spondylosis deformans or spinal stenosis), in which case you'd want to use Du Huo Ji Sheng Tang or Lumbrex.
Xiao Chai Hu Tang may be redundant if you're using DM Formula. You'd be better off bumping up the dose of the DM Formula.
There are home DNA tests available in Canada to diagnose vulnerability to DM. I'd encourage the owner to get one done. If it was negative, then Voltrex, Lumbrex and the like would be more likely to be helpful
Hopefully that helps!
Steve