Illness/Sickness: My newt lost a leg

Hi, I recently got a pair of newts for my 4 year old daughter because she really wanted a lizard. I have decades of experience with fresh and saltwater aquariums but none with newts. Anyway, I bought the pellet food the pet store recommended and put the newts in a well established tank that used to hold guppies. The have driftwood and a dense blanket of floating plants they can climb out of the water on. I also tried to google newt care and didn't find much info that looked reliable.

I think the newts tried to eat each other because within a couple of weeks one was dead and missing a couple toes and the other had a huge chunk out of his leg. That newt is still alive but the arm fell off and is now a large white patch (its not fuzzy). I switched to feeding him crickets at the advise of a different pet store and he seems to be plumping up and is a little more active. Will his leg regrow?

Could you maybe ad a photo or two of the newts so we can see?

feed him worms. live worms. newts don't like pellets.

The leg will regrow, provided that infection doesn't set in. Some of your questions are in these FAQ:
Caudata Culture - Frequently Asked Questions