In all fairness, cats are well known for their fickleness about food. One day they love a brand or flavor, the next they refuse to touch it.
My current Korat fellow likes his food a bit too well for that nonsense, but the 2 tabbies I had before him would do things like that every so often and I wouldn't have thought anything of it...just them doing their thing again.
Doesn't excuse the dogs, but I can understand with the cats.
There is such a thing as a finicky dog as well...
I've never owned one, mind you, but I have friends swear to me they've had dogs who won't eat. :~D