I suspect you are in a vicious circle, in that the kittens are gorging when food goes down because they are hungry, and because they have gorged there is nothing left and they become overly hungry before the next mea.
The vet has not said that they are overweight, so I would suggest that you try a completely different plan for the next 2-3 weeks (it will take that long for them to reset their 'training' to date)
Give half a sachet of wet food morning, lunchtime and night. Plus Leave dry food down the whole time. Refill the bowl if you see it is empty.
This will result in a lot of dried food being eaten in the first day or two .....but will then settle down to what they actually need, because kittens of this age rarely eat more than they need, if the food is not restricted. Also, buy a plastic tub and mix the current kitten food with new adult food....50/50. It is not a waste of money, because the whole tub will be eaten, but you will not be exclusively feeding substantially higher calorie food.
Each time i take my 5mo kittens to the vet, they comment on how much weight they've put on. Last week, the male weighed 2.8kg; the female 1.8kg. They're not classed as overweight, but they are putting the beef on at a rather worrying rate.
The thing is, they gorge their food when they get it, as though they are starving. And then I've already given them their day's worth of food, they meow all night for more, but I can't give them more or I'll end up over feeding them.
And now that my male has been neutered (last week) the vet said I should be giving them even less food. She's also recommended i switch them to a special neutered cat Canin food, but since I've got a gigantic bag of the normal kitten Canin left, she said I should use this first, but just give less because it's high calorie.
Anyway, I give them each 15g of the Canin kibble in the morning. 15g each at lunchtime. 15g each at dinner time along with 1/2 pouch of wet food (just for a bit of variety) then i leave 15g each down overnight.
So in total, they're getting 60g of the kibble each plus 1/2 pouch of wet food each per day.
That's the plan anyway, but they eat it up before i even go to bed, so they're hungry all night.
I've been trying to see online how much i should reduce their feeding to now that the male is neutered. But I can't see anything on the Canin bag or in their website. Any ideas?