I'm not clear on what you mean by "it sounds different." If it's gurgling you can take it off your battery and blow into the mouthpiece -- make use you hold a piece of tissue or paper towel at the other end to catch any liquid coming out of the center piece -- then wipe out the inside of the battery where it connects as well as the bottom of the clearomizer. That might do the trick.
The unknown here is the percentage of strawberry already in the nicotine mix. If it were me, I would set aside 10ml and slowly add other flavors to taste and note percentages of each as added. Just my 2 cents.