Innova is really not all that rich of a food (unless you're talking about EVO?) it was probably just something in the ingredients that didn't mesh with poor Maya's system.
Jackson didn't like the regular Innova. He just stopped eating it. Also, wanted to add, Innova and Natura products were just bought out by Proctor & Gamble, the company who owns Iams, etc. Many people stopped feeding for this reason. How long has this problem been going on? I wonder if they are changing ingredients already without people knowing.
In my humble opinion, I would try other higher quality foods than Purina before just giving up. Some dogs don't do well on certain foods but there's a lot of other options out there with way better ingredients ranging from lower proteins (Natural Balance comes to mind) to higher proteins (Orijen). Also, as for Butterscotch the dog, has he ever had higher quality food in his life? If the owner just randomly did a quick switch to Innova, with no week-2 week transition period, of course he's going to have diareah, his system is not used to it.
I'm not saying some dogs don't do well on Purina, Pedigree, etc. But I've seen so many older-ish dogs who have been eating that all their life and they are seemingly "doing just fine" and "perfectly healthy." My grandma's Lab, she will be 9 soon. Yes, she's got lots of energy and is a happy dog seemingly perfectly fine, but looking closer, she's got terrible breath, horrible teeth, sheds like a maniac (yes all Labs do, but food has a huge part in how much), she's overweight, she's got little bumps all over her and those scab-looking things on her elbows. I only notice these things because I've looked so much into dog nutrition.