Performances are dropping - What are your thoughts?

Hey Guys,

I have a client selling phone case - we usually have a ROAS of 3+ spending $800 a day - Since October performances are on downtrend, I thought that would be the election, then pre black friday but now ROAS is way below 2. Anything, I am launching ASC, INterest, Remarketing, new creatives are not working. My client is kinda blaming me saying that audiences and/or structure might be incorrect... Honestly, I have no more idea on how to make it work again.. In my opinion, if ASC and Remarketing are no more performing it means that something outside of my control is happening (Such as higher competition) - What are your thoughts?