Tracy,
It i not an issue to feed ground metformin in wet feed.
Your fine without the buffer in food, its not concentrated anymore and should not cause irritation.
Mine will eat 13 ground pills in 1 lb soaked cubes, less than that amout of cubes and she walks away but not mouth irritation at all.
--
Lesley Bludworth 
Phoenix, AZ   7/2022
Sophie TWH mare
https://ecir.groups.io/g/CaseHistory/files/SophieB%20Case%20History
https://ecir.groups.io/g/CaseHistory/album?id=277749