Log on webkinz. Just go away from the computer for a while, come back. Your pets stats should have dropped. When your not online, your pets' stats still drop but not as much. I didn't log on for about 2 days, and all my pet was dropped, a lot!
If you wait a week, Then your webkinz Status will drop and you would have to feed it and do activities to make it healthy. I don't understand why you even want too, Because if you want to make your webkinz sick that does not show it care, So that is being this-Respectfull to webkinz and your adopted pet. Also, Your pet is likely to not like you. If you would hate your webkinz character or avatar well then why did you even joined webkinz? It does not show auditional care to your pets and the company.