I have two axolotls that are a couple years old. One of the recently started displaying what looks almost like a skinned knee. On a couple of his legs, he has this red skinned look. He also seems more edgy (like things seem to startle him, such as my hand near the tank), isn't eating as much, and is floating at the top of the tank a lot. The other axolotl is completely fine and displaying none of these symptoms. Any advice on what it is or what to do? Thanks!