I put Advantyx on Roxie a week ago. I waited almost the week before giving her a much needed bath and today I see fleas on her. What is the deal with that? It's supposed to last a month and it hasn't been lasting that long all summer. But this time it's only been a week and I see them. I put it on exactly like your supposed to. I seperate the hair between the shoulder blades exposing the skin and put it directly on the skin. Why isn't it working? Should I be following up with flea spray or powder? I'm so frustrated!!