Better that it is in a thread of it's own - and I'll split it shortly.
Nutro isn't the greatest food out there, indeed. There is a 'Nutro Natural Choice Ultra' formula that recently made the Whole Dog Journal's list of quality foods - and the ingredient list on that one looks substantially better than the other Nutros.
As for going to Wellness, yes, it could be a good idea. If she's transitioned completely onto the Canidae now, I don't think it would make a great deal of difference - from a switching point of view - whether you're switching her back to Nutro or switching her to Wellness. Hopefully it will agree better with her tummy than the Canidae
I would certainly give her some pumpkin to try to firm those stools up in the meantime. If that doesn't work, you could feed her boiled chicken and rice - a nice bland diet like that should solve any problems. From there, I'd do the gradual thing with introducing Wellness - but if there are any runny stool problems, wait for them to firm up first before increasing the amount of Wellness in the food.