Death of brumating beardie. What could have happened?

[PitOnTheProwl]

She was one day over a year old (turned a yr on Jan 1). They didn't have a UVB light on to begin with but she had it on her for the last month.

Improper care. This was my first thoughts last night when I read the post but I didn't have time to post anything.
You also keep saying brumation however I think that was the sign of the start of problems.
My 5 dragons are between 3 to 5 years old and I have never seen any signs of what a typical brumation should be.
Then again they have a constant food source and do not have temperature swings as they would in the wild.