Just a tip on reading food ingredients since you're currently searching, Pat -
You said that the top 5 ingredients in Penny's current food are "turkey, chicken, barley, brown rice, and potatoes." My first thought is that this diet is probably very high in grains. The ingredient list has to be by order of weight in the food, and turkey and chicken are listed first and second, but they are listed without the word "meal" afterward. This means that they are added to the process as "whole," so the majority of the mass going into the food is water, which gets cooked right out. So really, nutritionally speaking, the major ingredients are the barley, rice, and potatoes, with the animal protein source (turkey/chicken) probably falling somewhere behind that. Adding the animal protein as whole instead of as a meal allows them to list it first.
So if you're looking for a diet lower in grains (to lower Penny's urine acidity) you want to find a kibble with a ___ (insert animal protein source) meal listed at the top.
Some of the grain free kibbles are great (Nature's Variety Raw Instinct is what I feed; I believe Solid Gold, Innova, and Timberwolf also have grain-free offerings) but watch the protein content if Penny is still growing. (Sorry, I don't know how old she is!) The protein content in these foods are not appropriate for young Newfs.
Good luck!
Tiff