Some of the symptons of columnaris match, some kind dont. It might be. How easy does that spread? So far no other fish show signs, just the pearls, and they are all gone now.
did you get the pearls all at the same LFS?
It sounds like you had a bunch that already had the virus and the virus became active after the couple of months in the new surroundings. Viral strains can be dormant for some time and re-activate due to stress or other variables. I am no doctor but after reading the posts, this is what it sounds like. Check with the LFS you got these from and see if any other pearls are having (or had) this happen to them.