Was he ever checked for parasites? If he's slowed down eating because of the winter (which can be normal), sometimes that will let parasite numbers bloom.

In any case, I'd stop feeding him dry foods until he's eating greens regularly. Whatever his problem is, he still needs to be hydrated.
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Torey
Eugene, Oregon, USA
1.1 Saharan Uros (Joe and Arthur)
3.0 Mali Uros (Spike, Turtle, and Tank)
1.1 Ornate Uros (Scuttlebutt and Shazzbot)
1.1 Collared Lizard (Ripcord and Rorschach)
2.0 Green Anoles (Bowser and Sprocket)
1.1 Chubby Housecats (Roscolux and Jenny)