oww change ehehe sorry..

hard to tell which vet is gud and nice with fair/cheap service/charge etc?..

need to know your location, and how much you normally pay for the services.

the only way is to see your cat and feel the body. i can't tell 4kg for 8 months is normal or not. because i need to see the cat size. some cat born with smaller body structure, some are big, some are shorter.

body length and size = body weight. both must balance.

touch the bottom part of the body, there should not be any hang over extra fat.
the hips must not visible.
back bone must be solid, not broader.
your cat is overweight if you cannot feel the ribs.

you can check this 2 articles:
Is my cat overweight?
Feeding your cat the right way.

the best way to ask your vet, when you bring your cat for vaccine or deworm, they will weight your cat. and see the different from last visit