I use the term "slip ups" politely.
Last week in Matalan, man at the tills with his family had pulled his mask down to his chin. Another woman walking round the store with it pulled under her nose so her moutb was covered but nothing else.
Yesterday a couple in an antique shop both pulled their masks down then took them off whilst walking around the shop. I get very huffy and loud every time I see it but what I really want to do is call it out and ask them to "put the mask on properly or leave the shop". Is it just me? Does anyone have any witty suggestions of how to suggest to people that they follow the guidelines properly for the good of everyone?