well from what you posted it may be nothing to worry about or it could also be a sign of a problem.
best thing is to take the dragon and a fecal sample to a vet.
the vet can then determine if the dragon has any parasites.
often a bd that has a load of cocidia will first seem lazy and start hiding out ... it happend to my bd during the first year.
BUT it can also be that if the hours of light are less than 14 and or if the bd can see sunset times or if the night time temps are starting to get lower he may just know it's fall and start wanting to sleep more. often a real "burmination" will not happen the first year; but that is not always the case.
the dragons size, health, genetics and the environment all play in this.... If for example it's a dragon that has grown fast and is healthy and sees sunset and lower night temps he may just have a light case of burmination the first year.
so get a vet to do a fecal and see if you need more light or to rase night time temps a bit.
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