I have 6 small clown loach. I bought them all at the same time around 2 inch apiece. They're all very active little fish and they all feed well at feeding times. Therefore i'd expect their growth rate and appearance to be similar. However, one of them is a good half inch bigger than the others already and his depth and girth is somewhat bigger too. The other 5, as happy as they seem, and as well as they eat, are showing signs of what i can only describe as this skinny disease that i've read about. They are very slender and have that tell tale sunken ridge along their backs. Is this an inherent thing with clown loach, will it gradually pass, do i need to treat it and why does one of them seem totally immune to it?