6 months is rather young for brumation. I would double check my temperatures, make sure the basking spot is getting high enough (around 100F) and the lights are staying on long enough. I would also bring a fecal to the vet to make sure he isn't having problems with parasites.
My bearded dragon was about 10 months when she decided to brumate but I made sure it wasn't anything else. I beleive it was caused more with the fact my appartment was cooler than it had been with the onset of winter. The place I was in didn't have very good insulation and I couldn't afford to have the heat on full blast to fight against the drafts. She slept fine through the winter though.
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PHLdyPayne