Will the red spots come off if you blow on them? If so they are most likely dust from the mulch. If not, they could still be mites. Soak your bearded dragon and see if the red spots come off. Mites will drown if immersed in water. Once they are dead, you can use a magnifying glass to get a better look at them. Or if you have a microscope that will be a better way to tell what they are.
If they do turn out ot be mites, you will have to completely clean the cage, soaking it in hot soapy water to drown any lose mites. You may have to do t his every week, tilll you see no more mites, or purchase any of the reptile safe mite sprays, such as Prevent a Mite or Reptile Relief. You can also take your dragon to the vet, and he can find out just what kind of mite/tick it is and recommend treatments.
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PHLdyPayne