my kittens they are 3 almost 8 months if this month will complete one of them is bigger them other 2 hes 3.900 kg almost 4kg but other 2 are 2.800 and 2.900 why? Hes active cat but little chubby and the mother cat weight is 3.200 and father 3.700 mother cat is small in height but father cat is bigger then mother cat is it normal that they are less then the kitten? When we went for checkup vet said they are healthy and weight is normal