Were they download apps? I know Google has been making a push to bring security back and they've forced a couple of devs for apps that I use to make changes or be pulled. That was just this week. Your app devs could have been caught up on that or they simply may have pulled their apps. Years ago I tried a few of the download apps and about every 5 months or so they would completely vanish as if the app has never been on my phone or in the app store. So they could have been caught up that way. Although no one reads the TOS for the apps they download devs can pull their apps off your device without notice.