Very cute beardie! 
It very well could be brumation. Last year my male went down at the end of august, early september (basically, around this time
he isnt showing any signs whatsoever right now though this year yet) I always take him for a vet visit when he starts to show any signs of brumation, like yours is now. I do it just in case it may be something else, and gives me peace of mind so that I know nothing is wrong. Has yours ever brumated before?
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~Melissa~
1.6 Leopard geckos
1.1 Bearded dragons
1.0 Hog Island Boa
0.1 Western hognose
0.1 Coastal carpet python
1.1 Crested Gecko
1.0 Savannah Monitor
0.0.1 Sulcata tortoise
1.0 Eastern Collared Lizard
1.1 Ferrets
0.1 Chinchilla
2.0 kitty cats