Several months ago I had problems with my guys itching (scratching their ears, licking/biting at their feet, etc.) so I switched them to Natural Balance Sweet Potato and Fish. The itching quickly subsided and pretty much went away all together.
Now they have started itching again.
Is it possible that they have come immune to this food and I switch them to another Natural Balance formula?
ETA: And if I should switch, any suggestions for a formula?