As they are all un-neutered there is a high risk of them having caught Feline Immune deficiency or feline leukaemia...which would make them more likely to pick up flu & eye infections etc...
Please for their sake get them tested & neutered, or you will just keep producing unwanted litters who might be carrying these very infectious diseases & passing them on to other cats. The Cats protection & also the RSPCA do schemes to help those who can't afford the neutering fee. In the short term, please get these cats to the Vet & don't leave them suffering...if it's got to the stage that they are struggling for breath it might already be too late, I hope it isn't.