Look at your placements - is it possible there could be accidental clicks?
Look at your placements on a tablet and a smart phone - is it possible there could be accidental clicks there?
Look at your traffic sources. Just because your topic was in the news doesn't mean that all the traffic would be considered good, converting traffic. I was working on a site once where we got a HUGE spike of traffic because one of the topics of the site (the title of a movie) was a clue in the New York Times crossword puzzle, and people were looking it up to do the puzzle (side note - a TON of people cheat on crossword puzzles!) That probably wouldn't have been considered very good targeted traffic for an advertiser, as it would be unlikely to convert and just arrived by a fluke. I don't know that for sure, because that was before they started clawing back, but that's my theory.
But look at your placements first. Specially if it was a news topic that brought your traffic, check how it looks in mobile. If your ads are somehow overlaying your content on small screens (or even just too close) that could be the issue.