Did the yellow fungus info look at all familiar?
Does he have a hide in his cage?
Another thing that comes to mind is brumation but from everything I've read the beardies aren't supposed to be that active during brumation, even a semi-brumation.
I've also read a couple of other people here indicate their dragons have been acting kind of funny about appetite without any visible signs of illness. It's been attributed to the strange weather this winter.
I can tell you my dragon hasn't had as much of an appetite for the last month and hasn't lost any weight at all. But he's been eating at least a good amount every other day and still goes about every other day.
What exactly do you mean about the skin being dry? If you pinch a small part of it on the side does it appear to stay pinched or go back to it's normal shape??
I'm not sure about the hard part you have mentioned but I think it's just a part of his intestine, maybe where there's a urate waiting to be expelled.
Have you tried soaking him in warm water for about 10-15 minutes?
When you mentioned it was like he urinated was it just liquid? Have you seen any urates (white material) when he goes?
Was the hard part off to one side or just in the middle?? If it's off to one side it may be a kidney and that may have something to do with the "urination" you saw.
What kind of supplements have you given him in the past? Does he have access to UVB? What are you temps at, both basking and ambient?
I'm just taking stabs at all of this but any of the above questions you can answer will help others who know more than I do figure out what's going on. Especially if you tell more about your setup.
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Rob Talkington