The product you used had nothing to do with why there were ticks on one but not the other. It is due to where they were walking. Because ticks are exoskeleton insects they dry up in the sun. If you are hanging out in the middle of the lawn you are less likely to get a tick on you than if you are out in the brush. Tics do not jump, they crawl to something that is tall and shaded and hope you go by and brush up against whatever they are on. Had the cav stuck to the pavement... he would have been tick free also. While both of those products do work...nothing is 100%. What did you use to pull the attached ticks off with? We have a few "Tick Spoons". They are a measuring style tea spoon with a beveled v-notch cut in them. The ticks scoop right out.