Catbrat, it could take a few weeks to a month, don't give up. You probably feel like you are taking 2 steps forward, then 3 three back, then 1 forward, etc. Remember, it's a living animal, not a machine. Patience is the key. You may find that after a month you cat just doesn't do Wellness, then you move to a different brand.
If we though that on food was good for all pets, then we would only carry one food, but we don't. We carry many, for this reason.