Ariana Grande -- Donut Shop Bombs Inspection ... After Licking Stunt

Just a couple flicks of Ariana Grande's tongue is all it took for that donut shop to get screwed -- it just failed a health inspection ... brought on by the video of her stunt.

The inspection report for Wolfee Donuts in Lake Elsinore, CA puts the blame for "donutgate" squarely on the employee who served Ariana and her BF. The report says the donut tray should not have been placed on top of the display case where anyone could access them.

Ariana's not mentioned by name in the inspector's report -- but it does reference the video TMZ first posted of "customers licking donuts incorrectly placed on counter."

A manager told the inspector the employee didn't know Ariana had tongued the goods, and "placed them back in display case for sale."

Bottom line ... the Health Department docked off one letter grade, leaving them with B rating. They have a week to fix the problems.