Pages and Numbers files suddenly opening very slowly on Mac

Starting today, on my Mac, Pages and Numbers files are opening very slowly from Finder. It has always taken a little time for them to open, maybe 2 or 3 seconds, but now it is taking much longer to open the same files, probably 10 to 15 seconds. Everything else is running fine. A re-boot did not change anything. I have done no software updates recently. I have a 2015 Mac-book Pro, 13 inch, with a Core I7 processor, 16 gigs of ram, and a 1 terabyte SSD which is only about a quarter full, so lack of system resources is not the problem. Does anyone have any idea what the problem might be and how to fix it?

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