I have a hatchling slider - I think he's a yellowbelly but I'm not completely sure. He was captured from a local pond a little over a week ago; when he was caught he was missing an entire front leg and it looks like he's missing part of his back foot on the same side. That really isn't a problem right now because he gets around very well in his tank, but I think it might have contributed to some other problems he has now. On his skin, especially his back legs, he has a lot of fuzzy stuff that floats around him when he's in the water. I am inclined to think that it is not just skin shedding because it is also visible when he is out of the water it looks like brownish goo. When I first got him I figured it was just some algae or residual pond muck that would clear up in a few days and that is why I haven't started worrying about it until now. It hasn't improved at all, so I think it must be some kind of skin fungus or something like that. Am I wrong? Advice would be appreciated. If it is, should I dry dock? I know that is what is done for shell fungus but I haven't been able to find much info about skin fungus. I'd like to know soon so I can dry dock tonight if needed.
Another problem that I don't think is very urgent but is kinda weird is that his shell is a very brownish/orangeish color instead of green like they usually are. His belly also has a lot of that color on it which is pretty odd. I figure that the weird coloration is due to malnourishment from him not being able to feed well in the wild since he's crippled. He is being fed well now with hatchling pellets, greens, insects, and soon some minnows. He has also been basking with heat and UVB and has ~80 degree water. He is very energetic and eats well so I don't think there's anything really wrong with him internally. If there is anything I need to know about his strange shell please let me know. Thanks in advance for any help you can provide

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I'm sorry I couldn't provide any pictures since I'm sure they would be helpful in diagnoses, but I don't have a camera right now.