I launched my app (https://play.google.com/store/apps/details?id=com.senstore.alice.harvard) about a year ago and it's performed very nicely, with an average review of 4.6. However in mid-december I started getting one 1 star review a day and over hte last month the average review score has dropped to 4.48 which has reduced my place in the charts. At almost the same time a new competitor arrived, and so I'm suspecting them of giving me the reviews. What should I do?