Google's Quality Score takes into account more than just your CTR; it also looks at how relevant your ads are and how well your landing page works. These things can change when Google changes its algorithms or when a competitor adjusts its ads. Check to see if your ad wording matches the keyword intent, and make sure your landing page speed and keyword match stay good. Even simple changes there can help your QS get back on track quickly.I noticed my QS dropped on a couple of keywords even though my CTR is stable and above average. Landing page hasn’t changed. Any idea why Google cuts QS when performance looks fine?