Just switched to Nature's Variety Instinct...

[CalistogaPyr]

I just switched Bo & Floyd from Natural Balance Duck & Potato to Nature's Variety Instinct (grain free).  I'm afraid I may have switched it too fast and upset Bo's sensitive tummy (my best intentions gone awry).  She's had cow flops intermingled with soft-formed stools for the past week (I started the switch last Friday).  Also, she's burping a lot and eating grass.  How long does it usually take for a dog to reach a baseline tolerance for new food?  I'm going to put some pumpkin & Slippery Elm Bark poweder in her dinner, so hopefully that'll help.  Does anyone have any other suggestions as to how to sooth the big girl's tummy? 
Also, has anyone else switched to this food?  What is your expereince with it? 
I appreciate the feedback!  I'm always on the look-out for good information!! =)
THANKS!
Well-meaning Jenn in CA!!

[People Whisperer]

I feed Lily Nature's Variety "Prairie" and "Instinct". I think it's great food and Lily really likes it. No gas no burping
Some dogs don't tolerate certain foods. Lily couldn't do Canidae, Merrick or Innova...she had terrible stools even when I was adding just a tiny bit of new kibble. Hamburger and rice give her REALLY bad diarrhea
It takes a while for pups to adjust though. If nothing changes in the next few weeks I would recommend looking for a different food

[lorim2]

I feed my lab NB duck and Potato.  She has done extremely well on this.  It totally stopped her food allergy throwing up and shes actually feeling great!  I didnt take to much time in the switching either because she was throwing up every meal.  She has done and continues to do very well on it.  Other than the price of it, I love it!

[CalistogaPyr]

I'm going to give it some more time to see if she "forms up".  My husband says I'm obsessed with Bo's poo!!  I'm hoping that she'll level out.  The amount of poo is considerably smaller than her usual cow flop, so hopefully that's a good sign!!  I think I get anxious when she's not feeling well and I want to fix it immediately, when the best thing is to just sit there and do nothing!! =)