>>Thank you sooo much! I have all those things on hand; even the tetracyline! (had to use it on the bettas for "popeye" a couple of months ago.)
Bad news. I looked him over more closely today (I haven't wanted to over-handle them) and found out that the white part isn't flesh, it's cartilage! On the very left edge of his left nostril is a vertical split. I don't know what the heck happened to him, but it's not fungus or just a flesh wound like I thought. It doesn't really look like there's any necrotic tissue around the area, so I don't think it's due to "rotting" or something. I suspect he just slammed his nose into the tank at some point before we got him and broke it! I noticed that when he breathes out there's often a wet bubble that blows out the injured side, so that worries me.
I had thrown a tiny bit of a tetracycline tab into the clean water I put in earlier today and he seemed a little more active after soaking/swimming in there for the day. (he's by himself in a plastic container for now.) When I checked him over a little while ago, I also noticed that he was shedding; it came off in my hand as he skittered around between my fingers.
Now I don't know if I should keep medicating him in the hope that it'll heal up, or if he won't recover from something like that!?
This guy (as well as his tankmate)isn't eating as far as I can tell; we've had 'em since Nov. 28th. I've given them small crickets, frozen bloodworms, frozen brine shrimp, and newt food. I even threw in the baby guppy we had left and neither of them have touched him; he's happily swimming away in the tank w/the healthier newt right now.
Anyone have any ideas? Oh, and to top it all off, one of our two little Northern Chorus frogs is on the lam! I noticed when I changed the water in the tree frog tank that he was no where to be seen. Took every piece of furniture out, including the substrate/liner. We turned the area around the tank inside out and upside down, but no frog. Sigh. I don't hold out much hope for finding him alive...it's really dry in our house outside the tank environs. And the cat roams the ground floor during the day.
They're in a terrarium that's a weird shape, so I had to improvise a top for it. Unfortunately, after 5 months of it working really well, it's suddenly not secure enough. Gotta figure out something new now, I guess. 
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Sprig - Head Keeper of the Mellen Menagerie: 1 cat, 2 garter snakes, 2 fire bellied newts, 3 baby red-eared sliders, 4 (uh oh, make that 3) little tree frogs, feeder fish and crickets... & a partridge in a pear tree! 