I had my dogs on CN for awhile a year or so ago and they lost interest in it too fairly quickly. I also noticed that their coat just wasnt as soft as it had been, and my shedding dogs, ended up shedding more. So I switched foods, problem was solved.
I have just started Tucker on NB canned foods to mix with his I/D dry and so far he seems to like it and is doing well. I have a bag and a half of the I/D left but when they are gone Im going to consider switching to one of their dry LID foods. Glad to hear Jackson is doing so good!!