My axolotl seems to have a chunk missing off the end of his tail. I noticed about a week ago that the end of his tail (the see through fin) had a small slice in it and thought it would just heal itself. Now instead of his tail being pointed its straight up and down. The fin on his tail seems to have receded to his tail. Hes white so i can see quite clearly that there is now no fin on the end of his tail. Will it heal itself or do i need to get something to put in the water? What do I do?!! please help.