All you can really do is quarentine him, collect a fecal and get it tested... If you think hubandry is not the issue, then the problem may be something that will turn up in his "poop." Whenever I see even the slightest indication their might be a problem... Continually sitting in awekward positions, dark-dull colors, lethargy, lack of eye shin (sunken eyes), edges of tail curled inward, ect. I assist feed them... Keep in mind that you may experience a couple of these things and their maybe no real problem... You have to take it all in context... It comes down to the fact that "know" the behavior of your animal, and you can sense when something just isnt right... To assist feed, I use chicken baby food, herptivite, reptocal, and pedialyte fed from a syringe... This is usually followed by a couple "shots" of straight pedialyte to assure hydration... Let us know how its going...
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Ben