sorry to hear that Fezz, i had the same problem a few years back, the backbones were curved over and the legs were more like flippers on a seal, when they were a week old they looked perfect, then this happened over the next two weeks, but i put it down to the fact that i had mated brother and sister,
hi mate they havint got the seal legs just the lump on the back . the hob i used is my mates and its not from this area so cant see it being a close mateing , just put it down to one of them things