I do think that is normal, Raiza. Some days Higgins just gobbles up any and all food that is put down for him and other days he just picks, picks, picks. But he's just as active as ever. I think there are days when they are just like us.....gobble, gobble or pick, pick. (Though to look at me, you'd know right away that I mostly gobble gobble...
)
I think they activity is the key. I've noticed that when they don't feel well, you can really tell by the decrease in activity and general mopeyness.