I got an idea which may not reflect well on my housekeeping, but I'll tell
you anyway.  Perhaps there is an organism in the cages which continues to
contaminate these 3 girls???  I decided to do a major cleaning of the cages
in an organized fashion which I hoped would kill everything that could be
invisibly growing in a cage.  All on the same day, I cleaned the cages with
bleach, rinsed them well, let them dry in the sun, soaked the carpets in
shampoo-filled water, rinsed them well, let them dry in the sun, and bathed
every ferret in Sebafon, rinsed them well, and let them run around like
maniacs to dry themselves (they don't care for the sun!).  So far, the
results are excellent!  I haven't washed their tails since I did the
cleaning (about a week ago) and both Eric and Rebecca noticed that they are
growing back the missing hair on their tails.
 
If it turns out my method didn't work after all, I'll let you know.  So far,
it looks as though something was living in the carpets or corners or
wherever which was never killed because I have never cleaned everything at
the same time.  I use real carpet on the ramps and small ledges, and these
don't get washed all that often, so perhaps that was the problem.  I wash
the bathmat carpeting I use on the full levels every two or three days,
along with their hammocks and bedding, but the real carpeting didn't seem to
get that dirty ....
 
BTW, it is true that my ferrets never smell bad, because I wash their
bedding at least twice a week.  Amazing what a difference it makes not to
wash them too often (except those darned tails!).  And no, washing them more
or less frequently made no difference in the tail problem.
[Posted in FML issue 1919]