I'm glad someone else brought this up, because I was thinking possible
lead poisoning.  It can cause anything from lack of appetite to severe
convulsions, and eventually death.  I'm not sure if a tox screen could
tell if this is the cause, so I would ask the vet to do a blood test
specifically for lead.  They can do that for humans - - and I see no
reason why it can't be done for ferrets as well.
 
In the meantime, please check out your ferret's food dishes.  Change
them out if you suspect them.  Also, make sure the paint in your home is
lead-free.  There are still some older homes out there with leaded paint.
I saw a few cases of poisoning in children while practicing as a
paramedic.  Make absolutely sure your ferrets couldn't have gotten into
any medication.  My little "angels" figured out how to get into our
medicine chest, and scared me half to death!  I've got a pretty unique
group of Houdinis and petty thieves, causing me to realize a long time
ago that ferret-proofing is an ongoing process.
 
I hope the babies improve soon.  More importantly, I hope a cause is
found quickly.  I know you're frightened.
 
Sincerely -  Jenny
[Posted in FML issue 4490]