absolutely you are right, just dim down the extractor and you will have the issue sorted. best way to go around it is to get yourself a grow room fan speed controller, something like the SM COM fan control and this has either the manual function or automatic one. Also consider spraying the plants and in this way you can add some foliage feed in the mix as well (i.e. Vita Race from Plagron)
One more thing...theoretically, the extractor fan has to work 24h...otherwise during the "night" you risk high humidity and mold in flowering stage. So maybe get a timer for the extractor as well so you can schedule it on/off when you desire, especially if you are working with CO2 suppliments as well.