When one campaign drags the average, check three things
First, check whether the campaign changed: new audience, new creative, new placement, or a budget increase that widened targeting. A campaign that scaled into broader, colder audiences will usually convert lower as volume grows, and that is a targeting story, not a store story. Second, check the landing page match: does the page show the promised product, offer, and price logic, with one clear next step, or does it send buyers to a homepage or generic page?
Third, check whether the weak campaign is weak on every page or only on one. If the same campaign converts acceptably on a dedicated landing page but poorly on a generic product page, the fix is the page for that campaign. If it converts poorly everywhere, including pages that convert well for other sources, the audience or creative is the likelier cause. That three-part check takes minutes and prevents a store-wide change for a campaign-wide problem.