The thing with Blue Buffalo (Diamond manufactured aside) is that it tends to cause vitamin overdoses in most dogs. Some dogs are fine with it, but a lot have problems. That and crystals, which are painful, especially in males.
As far as potatoes goes, it’s hard to find a grain free food that doesn’t use potatoes. It’s either white or sweet potatoes, peas, or legumes. Legumes are said to be harder for dogs to digest (how true that is, I can’t say). Most dogs are ok with potatoes, and most are ok with peas and legumes. Just likes with everything else, there will be dogs that have issues with certain things. The problem with the amount of carbs in kibble is that kibble needs a binder, and that’s pretty much what carbs are for. Some are better than others (corn vs sweet potatoes, for example) and not all carb sources are appropriate for every dog. And if you think about it, there’s really not very many grain-free carb sources out there. Potatoes are the cheapest, and neither potaoes or peas (or legumes) are bad options unless your dog can’t have them. I actually had to take one of my dogs completely off carbs because the yeast that naturally lives on dogs bodies would get so out of control that the poor guy would turn bright red and be so, so itchy. He’s still bothered by the grass, but he’s considerablely better since switching to all raw.
I would suggest switching through all different brands, and protein and carb sources regularly. Keeps life interesting for the dog, and keeps them from building up intollerances to certain ingredients in dog food, while also giving them a variety of vitamin and mineral levels, which helps prevent overdoses and deficiencies. Also lets you take advantage of sales 😉
