I am sorry to hear of your problems with the raw food and your 2 kitties seemingly to be getting turned off of it. Your issues seem to raise more questions that could give us a better handle on the problem. Your using the recipe of Dr. Pearson's and are you following it or are you making changes to it? The adding of too much heart or liver could also have a tendency of changing the flavor making a little more harsh, and not so palatable. Are you doing your own meat preparations in regards to grinding of the meat and bones? Is your meat grown locally or does it come from a factory farm, and hence the supermarket? Replacing the taurine with actual hearts is the best thing you can do. Our vet was saying that there are some issues with the man-made taurine seemingly causing some kind of skin issues, and she recommends going with the heart meat wherever possible for taurine. Are you still having loose bowel problems? If so it might be an idea next time you go to the vet take a fresh stool sample with you, and have it checked out for parasites.
I have found sometimes that the meat coming from the supermarket seems to have an off flavor that the cats can pick up on, and it makes it hard to persuade them to eat it. Could this be a problem? There is always a chance of there being an allergy to the chicken, but I wouldn't expect both cats to be affected that way. Their age at 8 months you would think would make it highly unlikely for being a allergy problem, but strange things do happen.
You might think of trying another meat like pork, it's a milder flavor than other meats, and the nutritional breakdown is very similar to a rodent, and there is no known allergy problem with pork. I will include to holisticat's website where you can see the recipe. I have been using the pork recipe for several years after having similar problems as you're having with chicken. As SCM mentioned have a wide variety of meat from time to time it helps to eliminate any allergy problems down the road. Chicken beef lamb, and I think Turkey all contain micro-digesting irritant which can cause inflammation in the digestive tract also leading to allergies, and irritable bowel problems. So it's a good reason to rotate your menus from time to time.
As far as cooking for the cats that's your call. As you know the best is raw, 2nd is if you cook for them, 3rd is canned, and kibbles rates last. If you're cooking stay away from the microwave. It does a major job in destroying the food nutrients from the radiation cooking method. I had a vet that gave me a hard time because I was using a microwave when I first started prepping food for Missy. I am enclosing a website for Food Data Search where you can correspond between raw and cooked meats. It'll give you wee bit of an idea on the changes in food between raw and cooked, and it doesn't start on the micronutrients like enzymes and chemical composition changes brought on from heat. The last website I use for doing my calculations for calcium and phosphorus in the cat's food.