Why do you believe that is a Spotted Gar? He may just be a Florida with an interesting pattern, or he may be a true spotted gar. Personally I believe that is a Florida, but it's also difficult for me to judge from the picture.
No your gars are fine. They may nip at each other but thats normal as my gars have torn or split fins regularly. I am currently keeping a 14 inch Tropical gar my Mystery gar at 9 inches and even a Alligator gar at 6 inches, along with some Shortnose gars around 11 inches.