Wellness is a great food. Zoe is currently eating large breed puppy although that might change due to some GI issues (yet another vet appt today). *issues are not because of the quality of the food, the vet suspects an allergy*
I worked for 5 years for a company that had me visited by dog food reps quite often and Wellness was always a company that was one of my favorites. (Nutro was always up there too in my mind for quality at an affordable price)
The best advice I could give is READ THE LABEL. I know this may seem simple but pet food companies use trickery quite often to fool the consumer into thinking they are buying the best for their pet.
For instance (and this seems to be the most often used) is this: You see a bag of premium dog food that has is big bold letters on the front, "Chicken- #1 ingredient!!". You only want the best for your furry friend so you flip over the bag and read the ingredients and sure enough chicken is listed first. (ingredient labels are listed in order of quantity). This is where alot of consumers get short changed.
This is the ingedient label: Chicken, whole grain rice, rice meal, egg, sweet potato, liver, rice starch.... and so on. See what they did? Usually they break up the second ingredient (sometimes third) into several "different" groups or parts so that chicken will be the #1 ingredient, but in reality when you add those three rice ingredients together... rice is #1 by a long shot. Most of the time they do this with either corn products or rice products.
Also, just because something costs alot or is a major pet food supplier doesn't mean it's the best. I am sure everyone remembers the pet food scare a few years back. To most peoples surprise their beloved premium food was being recalled and pulled off the shelf right alongside with the cheapest of grocery brands. This is when we learned that in order to cut cost some of the major premium companies hired outside canning companies that had virtually no quality control... killing so many furry family members in the process.
If you ever have any doubts or questions there are always resources available. The bottom line is that every dog is different and also its up to you to figure out what works for them or not. There are alot of good companies out there. If it's working no need to fix it.
Well I think I have been long winded enough.

I use to work in the industry so I know how these companies operate. I hope that I have helped in some way.