Welcome!!!!
Check the meat source of the Science Diet and see if it matches or differs from the Wellness. If it's different, you can see that Bernie likes that type of meat and is not diggin the Wellness. Chicken is most popular and if by chance both are chicken, I would try a different variety. If you email some companies, many of them will send samples. (See Sticky in this section) Also check kibble size,
sometimes if it's too large, Yorkies will turn up their nose. Snickers was so picky so I tried everything.
Good luck w/ Bernie