do you know for sure if this is something that has happened over time or if it was born that way? sometimes cresteds are born with slight genetic defects which could possibly be what this is.

has it had any injury to its feet/toes? i once had a juvie that got bit on the toes by a cage mate--two of its toes tried to fuse together as they healed and i had to take great care to separate the toes to make sure they didn't heal together. that doesn't sound too likely in your case though since this is happening on on more than one foot--unless there has been some kind of major shedding problem, which doesn't sound like the case either.

any chance you could get some pics? that might help determine exactly what is going on.