how to sustain download rates after first 30 days of launch

Im facing an issue in sustaining the daily install rate of my apps after 30 days of launch. Recently i am focusing more on developing applications for android. I had released few apps in the play store, some of them have recieved a reasonable response and i was able to get around 40K to 500K installs in the first month. But after that, the download rate started to decline and almost i receive only 20 to 30% of the downloads per day. I understand that in the first 30 days, my app ranked in many countries in top 100/10/5 but why it is lose charming after the first month. Even after i update the app with new features and bug resolved, it is never picking up to the initial momentum. I havent done any app promotion or marketing. Please share me some information regarding sustaining the app download rate.

After the first 30 days you can’t get into the Top new apps lists anymore, so you need to rely on user searches to get exposure.
My suggestion would be the try to get as much as possible +1 recommendations from your current user base, when a user +1 an app Google Play recommends that app to people in his circles, it might help you get the ball rolling again.

Thanks for your suggestion. I will try to get more +1 recommendations for the new apps that im developing.