I find that Jackson poops less, and more firm poops, while on grain-free. We did grain inclusive for a few months and he wasn't, like, a pooping machine but I am happier in general with his condition on most grain-free foods vs. grain inclusive (there's a few, however, that I'd still feed).
Have you ever considered trying grain-free? It could be that they are simply not fully utilizing some of the ingredients in the food, thus it all comes out
They may not need all the fillers.
I must say, even though I am not currently feeding it, Jackson probably had the best poops on Go! food (makers of Now! as well). Acana is another favorite.
I wouldn't say 3-4 is necessarily
abnormal; but I think 4 is pushing it. Jackson typically poos twice a day, occasionally three if he gets a lot more exercise.