eating pattern changed

both of my cats usually devour their food when I put it in their bowls, but now they seem to be eating less. They will go and eat very frequently, but not as much at once like they used to. This just happened one night when I put a little extra food in their bowls in the hopes they wouldn't wake me up to feed them so early. Well, this worked, but I'm just a little concerned about their change of behavior. I should mention that they are still eating the same brand as always (Natural Balance) but that it's a new bag. Could this maybe have anything to do withh it? Maybe an increase in certain ingredients or something? A long shot, but that's all I can think of. They also get some t/d at night which they eat most of before I wake up. Anyone have any thoughts on this?

The only other changes with them is that Mosley sometimes has a very slight stuffy sounding nose when she breathes. this happens rarely and is very mild.

also, Kinsey gets some brown crusty stuff in one of her eyes lately.

I posted these changes on the health forum also.

Does anyone have any thoughts or just to take them to the vet?

I would take them to the vet. URI do affect their eating habits because cats are smell driven, and when they are stuffed up they cannot smell therefore, they will not eat much.