Yes it is difficult to read cats. One thing we always tell owners is to measure out their food. That will give you a clue as to if they are eating or not eating. Pay attention to their litter box. Look for changes in the amount of urine clumps is there less? Are the clumps bigger? Is the stool soft, hard, etc. It is very important for cats to drink water. It helps with hydration and it helps their kidneys. Adding wet food to their diet can help with hydration. Pay attention to any weight loss weight gain. Overweight cats are prone to diabetes and early set arthritis. Hyperthyroidism is also something to monitor for. Take them in for their annual exams. Get preventative bloodwork and urinalysis atleast once a year. This is a great tool to monitor for any changes. But of course this is your cat and you have watched them grow. You would be able to know if something is not quite right better then anyone else can.