Hes looking great!!
Iwas going to say that it looks like another fish attacked him as i had a breeding once had a breedign pair of dwarf cichlids ( nannocar anomala) and overnight the female completely lost her tail (just like Lucky) really thought she was going to die. i know it was the male that did it to her!! but i put her in a breeding net in a larger tank ( that had good filtration) and within 3 weeks she was fully healed and swimming around just fine!!
Godd job Bettamomma!!