Wild felines are use to eating parasite ridden meat. Cats have been domesticated for thousands and thousands of years, lots of cats get sick and die from eating things they shouldn't outside. You sound very well intentioned and I'm sure you love your cats. I had to learn the hard way when one of my last cats got diabetes and needed shots of insulin twice a day, along with a veterinarian specialist with whom I consulted consistently to keep him healthy and alive. I learned a lot about keeping the little fluffy friends healthy and was probably doing exactly what you are doing now. Middle of the road hard food with free feeding? You probably just keep the bowl topped up and they graze whenever? Sounds about right if you have plump little fur baby. Look, I'm not trying to be mean or win Internet points at all. I fucking LOVE cats, like for real. My two babies are my fucking world. It's expensive, but I feed them the best grain free wet food I can find, and their treats are just freeze dried raw chicken and salmon bits. We give them a dry food very rarely when we are going to be away and miss a meal or two, if it's longer, we have someone that's stops by and gives them wet food. THEY LOVE the dry food, but it's really not healthy for them, seriously, ask any vet. I want the best for all our little furry friends and something that means listening to them cry for treats for twenty minutes and not give in, because I want them as healthy as possible to be around with me for as long as possible. They deserve! Your cats deserve it! YOU DESERVE IT FRIEND!