If your Tiktok  ads performance is dropping. There could be many reasons that are happening but one of them could be ad fatigue! That means that your ads have been shown many times to the same audience that they have become tired of seeing your ads. This results in your ads getting lesser views, lesser CTR and high CPM. If you are struggling with keeping your ads performance consistent. you can try; 1. Turning on automated ad creative optimization  2. Create an entire new campaign (including new adgroups) rather than duplicating existing ad groups into a new campaign that seems to help as well.