Fermentation temperatures have an impact on the characteristics of your beer. For examples some saisons like temperatures into the 90's. Trappists using the same yeast such as westamalle and westvleteren ferment at very different temperatures. It will all make beer. It will just have different characteristics. the beuaty of homebrew is you get to decide what you want. keep good notes of what actually happened instaed of what you wanted to happen so you can repeat what you want and change what you don't My guess is your yeast finished converting sugars take some readings