Can you make changes to your landing pages? If so, add content related to the keywords to increase the keyword score
You always go through the learning curve which costs you money, you will have to study a little to improve what you are doing
Keywords quality score can be increase by three ways good CTR, Keywords relevancy from ads and landing page and by maintaining keywords historical performance. When you first creating your campaign then keywords QS already good for some day by default then after Google starts analyzing performance of keywords and the keywords having low CTR and less or no relevancy with the ads and landing page getting poor QS and if you are not optimizing your campaigns then Google will stores your keywords performance in their database to calculate keywords performance history. So try to optimize campaign and get good CTR for the keywords, create keywords relevant ads and landing pages and maintain good performance history of your keywords.
I am completley agreed with Gopi Krishan. Thanks..... One factor might affect quality score i.e. ranking for that particular landing page position in Google Organic search.