I would put something in your rules or guide if you don't want things left in the fridge. Some guests really think they are doing you a favor by leaving behind their food for others. Unless its unopened most don't understand it goes right in the trash. I think people don't want to be the ones to waste it, so they leave it hoping someone else can use it.
My 4 star guests are those who asked a lot of questions and didn't bother to read they various and sundry lists, guides and emails we provide/ did not answer communication during the stay but did so before and after (communication) or those who left the place with crumbs on the counter and floor but not a major mess/required extra cleaning of a stove or area but nothing was truly egregious (cleaning). It goes down from there. If you were nasty in any way to me or my husband or extremely nitpicky and annoying you get a 3 or below, circumstance depending. If you left a big mess, damaged something and didn't tell us, didn't clean up after your dog, etc its 3 or below.
House rules is either 5 or below a 3. You followed them or you didn't. Some rules are more serious like having a bunch of unregistered people stay, burning things you shouldn't in our fireplace or fire pit, etc. The vast majority of guests follow the house rules just fine. I suppose there could be a 4 for some misunderstanding about a house rule that wasn't followed but I see that category as pretty black and white.