What are your views on zupreem ferret food, right now my fuzzies are on the terrible corn filled marshalls
i am thinking about switching over to zupreem also any suggestions on picky eater switching 
my two fuzzys turned their noses up to the treats i got them,raisins,spinach, and raw meat.

First, please no raisins.  Raisins have been know to cause kidney failure in dogs and ferrets.  Spinach is a vegetable, which ferrets don't and should not eat.  You can continue trying to offer raw meat as a treat.  You may have to gently "force" them to try it.  My ferrets have never liked beef but do eat chicken and turkey.  Other options are lamb, cornish hen and rabbit.  You can see if they'll take a chicken wing.  I would serve it at room temperature, as ours would not even try meat or soups made with meat right out of the fridge.  

My wife and I have fed ZuPreem Ferret Diet (NOT Grain Free) for 8  years, since we first got ferrets.  We mix it with 2 or 3 other decent kibbles.  They all like Zup and they have not had any diet related issues, other than 4 out of 23 developing insulinoma, and 3 of those were fed cat chow the first years of their lives.

THE DOOKS OF HAZARD

Everything UncleJoe said, LOL.

My personal recommendations for kibbles include Natures Variety Instinct, Wellness Core, and Orijen. 
Or a fully raw diet :-)

Ferrets: Wesley, Percy, Owen    -rip Bandit-
Bettas- Kitty, Pip, and Logan
Sun Conure- Kita
Gerbils- Piper and Tailer