I did that before posting here, and it did nothing.
INTERESTINGLY, I went to the Microsoft Store this evening and the lady who assisted me did a hard reboot to the Surface - press the start button and the up-volume button simultaneously. This apparently reboots the system. When it came up, I saw updates being loaded, and all of a sudden, the apps worked again! They are still working and I'm keeping my fingers crossed. If it happens again, the woman advised me to bring the Surface back and they would trade it out.
I will keep you updated - thank you for all of your suggestions!