Chances are that those apps had been moved to the SD card, and the SD card was removed unexpectedly somehow. This can happen if you removed the card without unmounting it first, or if the there's a problem with the card or the slot. You may have to uninstall those apps and reinstall them again. Also be aware that this could be a sign your SD card is starting to fail, so take this opportunity to backup that data to your computer or the cloud.