Fish tail!!!

[Fishlove]

Well one of my small orandas fish tail seems to be breaking away!! There are bits of it hanging and some of it seems to of disappeared! The fish in his self looks fine and is eating and swimming!! I was just worried as I don't no what has caused this! I also have two other fish and i am worrying that maybe one of them is trying to eat it as it is smaller than the others!! It has been suffering from White spot but I hav been putting the treatment in but there are still spots on him!! Any advice would help alot!
Thanks