Could just be you need to clean them with some cottonball and tepid water from the kettle-sometimes they get like this-coz mum cleans bums then eyes and so it makes them icky and they can get infected-keep cleaning them and the other kittys eyes too-clean from outside in-in one clean sweep-and have a word with your vet for some eye cream
If one kitty's got an infection you have to assume the other/s have too and treat accordingly
Wouldn't take it for catflu at this time