Illness/Sickness: Paddle Tail purchased without a limb?!?!

Hello all. My son and I went out a couple of weeks ago to purchase a new addition for the family tank. My husband and him have this as their project and bonding thing. At first he wanted a paddle tail but they didn't have one at our normal store. The manager called another store and found a fire belly at his sister store so off we went. When we got there, I looked into the tank and to my surprise there was a paddle tail! I have done a bit of research (not much mind you) on them and on fire bellies and they are pretty similar as far as temp, foods, etc. They were living in the same tank and have been for a while the clerk said. So since my son was set on the fire belly after seeing a picture, and I was set on the paddle tail, we decided to take both of them. Once we got home and we acclimated them to the water, and we set them free in their new home, we noticed that our adorable paddle tail was missing a limb. I have heard of some pretty bizarre circumstances where salamanders can regrow their limbs. He seems to be over the shock of loosing the limb and he is also eating well. We are not able to keep blood worms or small feeder fish in the tank EVER between the newt, salamander, and frog. So my question is how do I tell if the severed part is healthy or not? I have attached a couple of pictures of Fuerte (our paddle tail), I hope they help.

Hello there.
First of all i have to say, the mix you have in your tank is...well....a bomb waiting to explode.
Different species of newts shouldn´t be mixed. Very specially when we are talking about Paramesotriton (your newt is not a paddletail, but a warty newt....damn common names) and something else. Paramesotriton can be agressive, even between members of the same species.
The crab mixed with the newts is another really dangerous mix.
I would separate each newt into their own single tank. One species, one tank.
There are several reasons, apart from agression, why mixing is not your best option at all.

About your warty newt...it probably lost it´s leg in a fight with another newt(as i said, they are agressive). If it has cotton like stuff around, it´s infected. Check if it changes from one day to another..if there is no change at all, then it´s very possible the wound is healing and the leg will regrow.
Keep the animal cool. That will prevent the fungus/bacteria from growing too fast, and will keep the newts inmune system in shape. A temp of 15ºC or so would be good.

The wound looks pretty clean to me, but keep an eye on it.

Again, try to separate your animals into individual tanks as soon as possible, it´s in your best interest and the animal´s.
Good luck

I agree, it's a warty newt, not a paddletail. I chatted with MommaKitten on the chatroom, so she's been advised of the dangers with the animals that are mixed. Here are the links to the information I told you about in the chat. And a few others with info on treatments for newts. I hope you can get your husband/son to read this.
http://www.caudata.org/cc/articles/Mixing_disasters.shtml
http://www.caudata.org/cc/articles/escape.shtml
http://www.caudata.org/cc/articles/sores.shtml
http://www.caudata.org/cc/articles/illness.shtml