In some answer for the ferrets person who wondered what's going on with
the high blood creatinine levels, a webMD search gives this statement
(copied, pasted)
 
"Creatinine is produced at a steady rate and is affected very little by
diet or by normal physical activities.  If your kidneys are damaged and
cannot function normally, the amount of creatinine in your urine
decreases while its level in your blood increases."
 
Since one form of looked-for damage is from drugs, and Not all the
ferrets are on (or possibly none) any drugs, this might be ruled out.
However, one thing they all would be getting is water.  Tap water in
many areas where industry is dumping mercury and many other insoluble
pollutants into our watershed as well as actual drugs flushed into the
city water systems and not filtered out of it (this was documented on
several news-magazine investigations), should be switched for purified
or even distilled water to which you can add drops of your own health
boosters, if you need.  But mainly, if the ferrets are getting tap water,
and "suddenly" all of them are ill of something at once, cut out the tap
water and only fill their bowls, cups and water bottles with purified or
distilled water.
 
This we've done for all our shelter ferrets and it has been a big factor
in their increased life spans.  In a few more days, Jazzmine Miss Boss
Ferret will be an astounding fourteen years old.
[Posted in FML issue 5105]