Russ,
 
First the disclaimers.  I am not a vet.  I am not a Vet tech.  My wife an I
have been running a shelter for the past 14 months.  We've adopted out about
140 and have 16 of our own.  That's my experience base.
 
From what you've told me, I think that your first guess - new diet- may be a
good one.  We've seen that in *many* ferrets.  It's gotten to the point that
we make a mix of the three most popular foods in this area and feed that to
the ones we don't know what they've been eating.    Even then we often get
the loose, green, mucus stools.  We keep them hydrated and give them 1/4 tsp
of Pepto Bismal for about 10 days or until the stool firms up (usually less
than 10 days).  A very high percent seem to react to new foods in that
manner, and even putting them back on their old diet doesn't turn it off
right away but just seems to upset them more.
 
Again, remember the disclaimer and trust your vet.
 
Dick B.
[Posted in FML issue 1028]